--- a/FC-handset-spec	Mon May 09 03:59:24 2022 +0000
+++ b/FC-handset-spec	Tue May 10 06:00:13 2022 +0000
@@ -284,7 +284,7 @@
 problem seems difficult, but an elegant solution has been found.
 
 LCD backlight LED current will be selected by way of two Calypso GPIO pins
-configured as outputs, and a 74LVC2G125 dual tristate buffer.  Each tristate
+configured as outputs, and a 74LVC2G126 dual tristate buffer.  Each tristate
 buffer's A input will be tied high, and the two Calypso GPIO outputs will be
 connected to buffer output enable inputs.  There will be two resistors with
 different carefully computed values, each connected between one of the two
@@ -299,12 +299,20 @@
 LED.  The difference between the 15 mA maximum and the small dimmed mode current
 will be split unequally between the two switched SET resistors, allowing a total
 of 4 different backlight intensity levels to be selected via the two Calypso
-GPIO outputs going to the 74LVC2G125 buffer's output enable inputs.  The actual
+GPIO outputs going to the 74LVC2G126 buffer's output enable inputs.  The actual
 currents will be determined after some further experimentation with our lunalcd2
 test setup: this setup features our KWH020ST23-F01 LCD, a MAX1916-based
 backlight circuit, and a DIP switch pack selecting the LED current in 1 mA
 increments.
 
+74LVC2G126 has been chosen as the dual tristate buffer part instead of more
+common 74LVC2G125 because the '126 has active-high output enable inputs, making
+the software interface (bits in the GPIO output register) more intuitive: with
+a '126 buffer, writing 1 into GPIO11 or GPIO12 will turn on the corresponding
+current contribution, whereas a '125 buffer would produce an inverted sense.
+74LVC2G126GT parts were less readily available than the '125 counterpart, but
+we have now made a lifetime buy of the preferred part.
+
 1.4.5. Slight regression relative to Pirelli DP-L10
 
 The actual LCD backlight LED driving circuit inside the Pirelli phone is not