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doc/FTDI-EEPROM-tools: article started
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 22 Apr 2019 19:32:31 +0000
parents
children b2e9a6f3c833
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45
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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1 Mother Mychaela has developed a set of Linux command line tools for manipulating
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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2 configuration EEPROMs that are attached to FT2232x devices and accessed in-band
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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3 via USB. This document describes these tools.
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Mychaela Falconia <falcon@freecalypso.org>
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4
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Mychaela Falconia <falcon@freecalypso.org>
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5 Supported FTDI chips and EEPROMs
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6 ================================
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7
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Mychaela Falconia <falcon@freecalypso.org>
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8 The present tools work with 93C46, 93C56 and 93C66 EEPROMs attached behind
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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9 FT2232x dual-channel UART/FIFO/MPSSE/etc chips, both FT2232C/D and FT2232H.
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Mychaela Falconia <falcon@freecalypso.org>
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10 We can read these EEPROMs for examination or backup, and we can program them
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Mychaela Falconia <falcon@freecalypso.org>
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11 with new bits, either restoring a previously saved backup or creating a new
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Mychaela Falconia <falcon@freecalypso.org>
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12 from-scratch configuration. These EEPROM configurations (which we can save,
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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13 restore or create from scratch) set the USB VID:PID and the textual strings
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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14 naming the manufacturer, the product model and an optional serial number,
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Mychaela Falconia <falcon@freecalypso.org>
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15 select whether each FT2232x channel will come up in the default UART mode or
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Mychaela Falconia <falcon@freecalypso.org>
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16 one of the other EEPROM-configurable modes (245 FIFO, CPU-style FIFO or fast
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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17 opto-isolated serial), and allow a few other obscure chip settings to be
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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18 tweaked.
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19
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20 Some work has also been done toward the goal of being able to program the
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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21 internal EEPROM in FT232R chips (a very popular single-channel USB to UART
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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22 converter needing no external components), but this work has not been finished
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Mychaela Falconia <falcon@freecalypso.org>
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23 yet, and the present tools should NOT be used to attempt an EEPROM write on
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Mychaela Falconia <falcon@freecalypso.org>
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24 that chip - the risking of bricking the chip is too high.
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25
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26 More generally, our fteeprom-read tool should be able to read out the EEPROM
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Mychaela Falconia <falcon@freecalypso.org>
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27 content from just about any FTDI chip including FT232R, whereas our
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Mychaela Falconia <falcon@freecalypso.org>
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28 fteeprom-prog tool should be able to program a user-supplied set of bits into
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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29 any FTDI+EEPROM combo where the EEPROM is a separate chip - but it is NOT safe
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Mychaela Falconia <falcon@freecalypso.org>
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30 to use on FTDI chips like FT232R or FT-X that have their EEPROM built in.
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Mychaela Falconia <falcon@freecalypso.org>
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31 Furthermore, if the goal is to generate a new EEPROM config from scratch, as
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Mychaela Falconia <falcon@freecalypso.org>
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32 opposed to restoring a saved backup, we currently have generators only for
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Mychaela Falconia <falcon@freecalypso.org>
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33 FT2232C/D and for FT2232H. (We also have a generator program for FT232R, but
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34 it is of no use for as long as fteeprom-prog is not safe to use on FT232R
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35 chips.)
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36
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37 libftdi dependency
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38 ==================
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39
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Mychaela Falconia <falcon@freecalypso.org>
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40 We use libftdi (which is in turn layered on libusb) to issue the special USB
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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41 control pipe commands to FTDI chips which are needed to read and write their
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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42 EEPROMs. We use old-style libftdi-0.x (-lftdi on the link line) as opposed to
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Mychaela Falconia <falcon@freecalypso.org>
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43 libftdi1 (-lftdi1) because the new versions took away the ability to write to
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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44 the EEPROM directly with ftdi_write_eeprom_location() calls, forcing users to
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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45 go through libftdi1's own EEPROM smarts, which we don't want to do - our tools
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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46 are all about more direct user empowerment at the lowest level.
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47
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48 Selecting the device to operate on
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49 ==================================
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50
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Mychaela Falconia <falcon@freecalypso.org>
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51 Our fteeprom-read, fteeprom-prog and fteeprom-erase tools take a device selector
1f3a4115375f doc/FTDI-EEPROM-tools: article started
Mychaela Falconia <falcon@freecalypso.org>
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52 argument, selecting the device to operate on. This required argument is the
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Mychaela Falconia <falcon@freecalypso.org>
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53 string to be passed to the ftdi_usb_open_string() function in libftdi, allowing
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Mychaela Falconia <falcon@freecalypso.org>
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54 the device to be operated on to be selected in one of several ways. Copying
1f3a4115375f doc/FTDI-EEPROM-tools: article started
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55 from libftdi documentation, the available formats are:
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56
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57 d:<devicenode> - path of bus and device-node (e.g. "003/001") within usb device
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58 tree (usually at /proc/bus/usb/)
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59
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60 i:<vendor>:<product> - first device with given vendor and product id, ids can
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61 be decimal, octal (preceded by "0") or hex (preceded by "0x")
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62
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63 i:<vendor>:<product>:<index> - as above with index being the number of the
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64 device (starting with 0) if there are more than one
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65
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66 s:<vendor>:<product>:<serial> - first device with given vendor id, product id
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67 and serial string
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68
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69 If you have only one FTDI device connected to your PC or laptop at the time of
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Mychaela Falconia <falcon@freecalypso.org>
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70 your EEPROM manipulation session (generally a good idea to avoid hitting the
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Mychaela Falconia <falcon@freecalypso.org>
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71 wrong device by mistake) and if that FTDI device has some sensible starting
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Mychaela Falconia <falcon@freecalypso.org>
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72 USB VID:PID (either from the previous EEPROM config or the chip's sans-EEPROM
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Mychaela Falconia <falcon@freecalypso.org>
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73 default) that doesn't clash with anything else, then the i: form will probably
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74 be the most convenient, e.g.:
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75
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76 i:0x0403:0x6001 for single-channel FT232x devices running with the default ID
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Mychaela Falconia <falcon@freecalypso.org>
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77 i:0x0403:0x6010 for dual-channel FT2232x devices running with the default ID
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Mychaela Falconia <falcon@freecalypso.org>
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78 i:0x0403:0xPPPP for custom PIDs assigned out of FTDI's VID range
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Mychaela Falconia <falcon@freecalypso.org>
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79 i:0xVVVV:0xPPPP for totally custom USB IDs
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80
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81 Or if the current device config is totally hosed (the EEPROM has a passing
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Mychaela Falconia <falcon@freecalypso.org>
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82 checksum, but sets some completely bogus USB ID), then the d: form will
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83 probably be required for recovery.
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84
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85 Reading the EEPROM
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86 ==================
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87
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88 The basic EEPROM read command is as follows:
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89
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90 fteeprom-read <device-selector>
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91
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92 See the previous section for the device selector argument. In this default
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Mychaela Falconia <falcon@freecalypso.org>
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93 form the tool will read the first 64 EEPROM words, which is appropriate for
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94 93C46 external EEPROMs or for the internal 1024-bit EEPROM in the FT232R chip.
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95 However, if you are working with an FT2232x board with an external EEPROM and
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96 that EEPROM is of a larger variety (93C56 or 93C66), this basic form with give
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97 you an incomplete (truncated) read, and you will need one of the following
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98 extended forms to read the complete EEPROM:
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99
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100 fteeprom-read -b <device-selector> -- read 128 EEPROM words (93C56)
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101 fteeprom-read -B <device-selector> -- read 256 EEPROM words (93C66)
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102
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103 (If you use one of the extended forms on a smaller EEPROM, you will get 2 or 4
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104 copies of the same bits.)
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105
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106 The output of fteeprom-read is in the same format as the input to fteeprom-prog,
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107 thus you can redirect the output to a file and get a restorable backup copy of
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108 your EEPROM.
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109
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110 Programming the EEPROM
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111 ======================
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112
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113 In terms of the primitives provided over USB, writing to EEPROMs behind FTDI
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114 chips is accomplished by writing one 16-bit word at a time: the
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115 SIO_WRITE_EEPROM_REQUEST command writes a user-supplied word at a user-supplied
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116 EEPROM address. However, our fteeprom-prog tool currently supports only writing
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117 complete EEPROMs (64 or 128 or 256 16-bit words starting at address 0) and we
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118 do not currently provide any kind of "random access write" utility; the primary
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119 reason for this design decision is practical usefulness: FTDI's EEPROM structure
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120 includes a checksum over the first 64 words for 1024-bit EEPROMs or over the
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121 first 128 words for larger ones, and if this checksum fails to match, the entire
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122 structure is deemed to be invalid - hence there is no practical use case for
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Mychaela Falconia <falcon@freecalypso.org>
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123 selectively rewriting individual words. The only exception may be with 93C66
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Mychaela Falconia <falcon@freecalypso.org>
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124 EEPROMs: on these giants only the first half would be subject to the checksum,
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Mychaela Falconia <falcon@freecalypso.org>
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125 and the second half could be used arbitrarily. However, we have not yet
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Mychaela Falconia <falcon@freecalypso.org>
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126 encountered any boards out in the wild with such big EEPROMs, and we have no
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Mychaela Falconia <falcon@freecalypso.org>
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127 plans to use such in any of our own hardware designs either, hence there is no
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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128 business case at the present moment to develop tooling support for them.