Nonpareil status

[brouhaha]

These are notes on the CRC reverse-engineering that Jacques Laporte and I did back in 2007-2008.

The CRC chip (Card Reader Controller) has twelve flags, which we've numbered 0 through 11. Our numbering may not match HP's internal numbering, which we were not privy to. Each flag has a set instruction, and a test-and-clear instruction (like the HP-41C FS?C), except that flag 0 can only be tested. Five of the flags control and monitor the card reader hardware:

* 0 buffer ready
* 7 data valid
* 9 motor enable
* 10 card inserted
* 11 write mode

Four of the flags sense other hardware inputs, of which only one is used in the 67:

* 1 PRGM mode (67/97)
* 2 printer MAN mode (97), unused (67)
* 3 printer NORM mode (97), unused (67)
* 4 keyboard sensing for SST, BST, R/S (97), unused (67)

The other three flags appear to have no dedicated hardware function, and exist for the convenience of the person writing the microcode. The 67/97 use those for:

* 5 MERGE
* 6 PAUSE
* 8 display-related

The octal encodings of the instructions are:

0100 crc fs?c 0
0200 crc sf 1
0300 crc fs?c 1
0400 crc sf 2
0500 crc fs?c 2
0600 crc sf 3
0700 crc fs?c 3
1000 crc sf 4
1100 crc fs?c 4
1200 crc sf 5
1300 crc fs?c 5
1400 crc sf 6
1500 crc fs?c 6
1600 crc sf 7
1700 crc fs?c 7

0060 crc sf 8
0160 crc fs?c 8
0260 crc sf 9
0360 crc fs?c 9
0460 crc sf 10
0560 crc fs?c 10
0660 crc sf 11
0760 crc fs?c 11