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annotate ueda/doc/netlisting.txt @ 9:faeb83c43f1c

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author Space Falcon <falcon@ivan.Harhan.ORG>
date Sat, 01 Aug 2015 20:50:59 +0000
parents cd92449fdb51
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1 How uEDA tracks electrical interconnect (netlist) information
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2
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3 Whereas the MCL (see mcldoc.txt) is the authoritative source of information
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4 about all components making up a board design, information about the way they
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5 are interconnected is stored in the schematic sheets (.usch files) in the
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6 language described in uschemlang.txt. Electrical connections are declared by
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7 way of assigning component pins to named or unnamed nets and may or may not be
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8 represented graphically. The following two constructs in the uschem language
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9 connect component pins to nets:
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10
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11 * Net and GraphNet objects
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12 * PinToNet decorations on component instance objects
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13
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14 Whichever method is used (see uschemlang.txt for the syntax details), the
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15 declaration of an electrical connection effectively consists of the following
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16 3 parts:
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17
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18 * Identification of the component involved;
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19 * Identification of which pin to connect;
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20 * The name of the net. (Net and GraphNet objects can create unnamed nets -
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21 those connect together everything listed in the respective object, but
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22 nothing else can connect to such nets.)
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23
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24 While it's possible for the component identification to be equal to the refdes
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25 as given in the MCL and for the pin identification to be the "raw" pin number,
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26 uEDA provides two mechanisms that allow the interconnect information to be
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27 entered in a slightly more high-level form: component instances and pinout
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28 mapping.
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29
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30 Component instances
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31
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32 In uEDA a component instance is essentially a reference from a schematic sheet
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33 to a component in the MCL. In a graphical schematic each component instance
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34 would normally be represented by a graphical symbol, and all net connections
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35 made in schematic sheets actually refer to component instances rather than to
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36 MCL components directly.
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37
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38 For trivial components like resistors and capacitors as well as some simple
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39 ICs there is normally only one instance per component, hence the component in
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40 the MCL and the instance in a .usch sheet are one and the same for all practical
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41 purposes. However, for many of the more complex components it is generally
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42 desirable to break the component up into multiple sections (which may be
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43 identical or heterogeneous) represented separately in the schematic source code
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44 for the design. That's what the component instances in uEDA are for.
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45
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46 In the case when there are multiple component instances referring to the same
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47 component, these instances may appear either in the same schematic sheet or in
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48 different sheets. If a given schematic sheet contains only one instance of a
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49 given MCL component, regardless of whether or not there are other instances for
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50 the same component in other sheets, the instance name may be equal to the refdes
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51 of the component - that's what happens when the user doesn't make use of the
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52 component instance mechanism. However, if a single schematic sheet contains
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53 more than one instance for a given component, there needs to be a way to
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54 distinguish between them.
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55
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56 When uEDA tools process a uschem sheet and match it to the MCL, the following
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57 algorithm is used to match component instances to components:
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58
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59 1. All component instance names appearing in a given schematic sheet are
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60 required to be unique.
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61 2. Each component instance name is stripped of any trailing lowercase letters to
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62 obtain the corresponding refdes.
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63 3. Each refdes is looked up in the MCL - if not found, that is an error.
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64
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65 Thus if you need to put multiple instances for a given component in a single
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66 schematic sheet, give each a unique name consisting of the refdes with a unique
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67 all-lowercase suffix appended to it.
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68
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69 Pinout mapping
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70
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71 uEDA allows one to use two different alphanumeric strings to identify the
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72 individual pins of a component: pin name and pin number. Both are arbitrary
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73 alphanumeric strings (actually strings of any printable ASCII characters subject
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74 only to common sense limitations); the pin number string doesn't have to be
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75 purely numeric. (For example, PGA and BGA packages normally use alphanumeric
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76 pin numbers.)
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77
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78 Pin numbers are what appears in the final netlist output from uschem-netlist(1),
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79 and they may also be used in the schematic source code. If the source only uses
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80 pin numbers for a given component, then there is no need for uEDA to know the
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81 pinout of that component. However, uEDA also allows one to specify the pinout
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82 mapping for a component and to use pin names instead of pin numbers.
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83
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84 Pinouts are specified in dedicated pinout mapping files and brought into the
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85 design via pinout= attributes in the MCL. Pinout mapping files use a very
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86 straightforward format: each pin mapping is given on a separate line; each such
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87 line consists of two fields separated by tabs or spaces: the left field is the
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88 pin name and the right field is the pin number. Comments are marked by '#';
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89 all blank lines and comment lines are ignored. Any additional fields past the
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90 pin number are currently ignored as well, but this behavior should not be relied
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91 upon; any such line-appended comments should begin with a '#' character.
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92
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93 The name of the pinout mapping file specified in the pinout= attribute is only
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94 the base filename, not a pathname. uschem-netlist and uschem-print (the only
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95 two programs in the uEDA suite that need pinout mappings) locate pinout mapping
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96 files using the same mechanism that is used to locate graphical symbol files -
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97 see uschem-netlist(1) and uschem-print(1).
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98
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99 In addition to making the schematic source code more readable, pinout mappings
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100 make it easy to support components that come in several different packages with
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101 different physical pin numbers for the same logical functions. It is no longer
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102 necessary to create multiple versions of the same graphical symbols with
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103 different pin numbers embedded inside or to edit pin references in Net objects;
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104 instead all those references can now be made by the logical pin name. If a
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105 decision is made to change to a different package with a different pinout, only
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106 the pinout= attribute in the MCL entry for the respective component needs to be
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107 changed - at the same time when you change the manufacturer_part_number= and
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108 footprint= attributes.
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109
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110 By the same token it is no longer necessary to create special PCB footprints
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111 with logical pin names embedded in them where pin number strings normally go:
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112 instead one can take the natural approach of having footprints identify pins or
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113 pads by their physical position, having schematics and symbols refer to pins by
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114 their logical function only and using pinout mapping files to bridge the gap.
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115 The pinout mapping feature is one of uEDA's main advantages over gEDA.
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116
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117 Slotting
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118
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119 The concept of slotting (and the term) originates in gEDA, but uEDA implements
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120 it in a very different manner. uEDA's approach to slotting combines component
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
121 instances with pinout mapping in a special way. But first, what is slotting?
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
122
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
123 Suppose that you have a physical component (typically an IC) that consists of
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
124 multiple identical logical blocks such that each of those blocks should be
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
125 treated as a separate device in the schematic source code. 74xx logic ICs are
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
126 a classic example. When one needs to describe the use of such a component in a
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
127 design, it is normally desirable to represent each slot as its own component
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
128 instance and furthermore to do it in such a way that one doesn't have to decide
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
129 upfront which slot will be used for what, allowing slots to be reassigned with
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
130 ease.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
131
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
132 In uEDA this feat is accomplished by combining component instances with pinout
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
133 mapping. When each slot is declared as a component instance, all connections
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
134 to it are made by logical names only: for example, a NAND gate that is 1/4th of
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
135 a 7400 would have connections made to A, B and Y rather than to specific pin
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
136 numbers. So far, so good. But how would the tools know whether A for example
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
137 should be mapped to pin 1, 4, 9 or 12? That is where the slot= attribute comes
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
138 in. It is one of the few attributes defined in the component instance
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
139 declaration (Component object) in a schematic sheet rather than in the MCL.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
140 When uEDA tools map a pin name to a pin number for a component instance that has
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
141 the slot= attribute defined, the value of this attribute is appended to the pin
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
142 name after a colon, e.g., if the pin name is A and slot=1, the pin name looked
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
143 up in the pinout mapping table will be A:1. The pinout for a 7400 quad NAND
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
144 gate looks like this:
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
145
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
146 #pin name pin number
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
147 A:1 1
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
148 B:1 2
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
149 Y:1 3
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
150 A:2 4
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
151 B:2 5
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
152 Y:2 6
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
153 GND 7
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
154 Y:3 8
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
155 A:3 9
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
156 B:3 10
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
157 Y:4 11
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
158 A:4 12
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
159 B:4 13
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
160 Vcc 14
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
161
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
162 Note the GND and Vcc pins which are not slotted. It is perfectly legitimate to
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
163 have some component instances which have the slot= attribute selecting one of
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
164 the logic slots, yet have other component instances referring to the same
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
165 component (e.g., for the power pins) without slotting.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
166
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
167 The following pinout for an SN75LBC784 EIA-423 transceiver is a more complicated
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
168 example of heterogeneous slotting:
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
169
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
170 #pin name pin number
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
171 Drvr_In:3 1
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
172 Rcvr_Out:3 2
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
173 BIAS1 3
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
174 Drvr_In:4 4
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
175 Rcvr_Out:4 5
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
176 BIAS2 6
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
177 Vss 7
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
178 GND 8
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
179 Rcvr_In_N:4 9
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
180 Drvr_Out:4 10
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
181 Rcvr_In_N:3 11
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
182 Drvr_Out:3 12
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
183 Rcvr_In_P:3 13
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
184 Rcvr_In_P:4 14
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
185 Rcvr_In_P:1 15
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
186 Rcvr_In_P:2 16
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
187 Rcvr_In_N:2 17
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
188 Drvr_Out:2 18
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
189 Rcvr_In_N:1 19
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
190 Drvr_Out:1 20
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
191 Vdd 21
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
192 Rws 22
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
193 Drvr_In:1 23
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
194 Rcvr_Out:1 24
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
195 BIAS3 25
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
196 Drvr_In:2 26
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
197 Rcvr_Out:2 27
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
198 BIAS4 28
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
199
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
200 This IC has 4 driver sections, 4 receiver sections and a set of common pins.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
201 The pinout file given above allows it to be represented schematically using a
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
202 separate component instance for each driver section (with slotting), a separate
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
203 set of component instances for the receiver sections (an independent set of
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
204 slots) and one or more non-slotted component instances for the common pins.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
205
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
206 It is also worth noting that slot names (the value of the slot= attribute) are
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
207 not restricted to numbers only and may in fact be arbitrary ASCII strings. For
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
208 example, it would be sensible to define the pinout for a bicolor LED with slots
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
209 named "red" and "green", having complete pin names such as A:green and C:red
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
210 with connections being made to just A and C on the proper instances.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
211
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
212 Netlist generation
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
213
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
214 When uschem-netlist processes a set of schematic sheets and an MCL to compile a
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
215 complete netlist, it first resolves all pin names (with or without slots) to
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
216 physical pin numbers and tracks the connection information at the component
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
217 level, i.e., the information is effectively moved up from the instance level at
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
218 which it is specified in the schematic source code to the component level. The
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
219 netlist data structures constructed by uschem-netlist maintain a hard
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
220 requirement that every physical pin of every component listed in the MCL be
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
221 either connected to exactly one net or left unconnected; thus any attempt to
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
222 connect the same physical pin to more than one net will be detected and flagged
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
223 as an error regardless of how each connection was specified in the source code.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
224
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
225 One may use the NoConnect decoration on a component instance object to declare
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
226 explicitly that a given pin shall be left unconnected. uschem-netlist will note
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
227 such declarations and flag an error if an attempt is made anywhere else in the
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
228 source code to connect the same physical pin to some net.
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
229
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
230 Differences from gEDA
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
231
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
232 The main difference between gEDA and uEDA with regard to netlisting is that in
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
233 uEDA graphical elements such as symbols and net lines do not create electrical
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
234 connections, they merely illustrate them. The uschem language (documented fully
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
235 in uschemlang.txt) is designed so that the graphical information and the
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
236 electrical interconnect information are mostly orthogonal. The electrical
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
237 interconnect information must be fully specified in the .usch files, not
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
238 inferred from symbol files, to the point that the latter files are not needed
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
239 for netlist generation and are not read by uschem-netlist at all. Thus gEDA
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
240 constructs such as auto-connected hidden power pins have no place in uEDA; the
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
241 closest one can get to that would be to insert a non-graphical component
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
diff changeset
242 instance with the necessary net connections into an otherwise graphical
cd92449fdb51 initial import of ueda and ifctf-part-lib from ifctfvax CVS
Space Falcon <falcon@ivan.Harhan.ORG>
parents:
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243 schematic sheet.
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244
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245 By a similar token the graphical symbols for power rails and such do not cause
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246 a net to be connected to a rail, instead that connection is made by having the
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247 proper netname set on the GraphNet object in the .usch file; the symbols merely
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248 illustrate it graphically for those looking at the printout rather than the
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249 source code.
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250
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251 The downside with uEDA's approach is of course the very real possibility that
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252 the netlist and the graphics will get out of sync, i.e., that the set of
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253 electrical interconnections mentally inferred by someone looking at the
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254 graphical schematic printout will differ from the set of interconnections
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255 embodied in the source code processed by uEDA tools. See drc.txt for the
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256 discussion of how uEDA addresses this problem.