This is the microcode in a HP67 calculator that waits for a key press.<\/p>\n
\r\n00167: 0 -> s 3\r\n00170: CRC 1500\r\n00171: if 1 = s 3\r\n00172: then go to 0263\r\n00173: 0 -> s 1\r\n00174: CRC 300\r\n00175: if 1 = s 3\r\n00176: then go to 0204\r\n00177: if 0 = s 11\r\n00200: then go to 0206\r\n00206: 0 -> s 3\r\n00207: CRC 560\r\n00210: if 1 = s 3\r\n00211: then go to 1324\r\n00212: if 0 = s 15\r\n00213: then go to 0167\r\n<\/pre>\nIt spends most of its time in this loop just checking to see if there is anything to do.<\/p>\n
The addresses above are in octal. All of them are < 256 decimal so they are all in rom 0 of the first “quad rom” (one chip with 4 lots of 256 microcode instructions). Roms 0, 1, 2 and 3 are in the first quad.<\/p>\n
The CRC instructions are “card reader circuit” commands.<\/p>\n
CRC 1500 checks a flag in the card reader and if set, sets the s 3 flag in the calculator (and clears the card reader flag). I don’t know what the flag means yet but 0263 is likely to answer that.<\/p>\n
CRC 300 checks the run-w\/prgm switch. If you are in “W\/PRGM” then it sets the s 3 flag. It clears it if you are in “RUN” mode.<\/p>\n
CRC 560 checks whether a card has been inserted into the card reader. If so, s 3 gets set. If not, s 3 is 0.<\/p>\n
s 15 gets set when a key has been pressed. This suggests that 00214 onwards deals with a key press.<\/p>\n
s 11 is a mystery at present. If does seem to go into code that checks whether MERGE has been selected so it may be card reader related.<\/p>\n","protected":false},"excerpt":{"rendered":"
This is the microcode in a HP67 calculator that waits for a key press. 00167: 0 -> s 3 00170: CRC 1500 00171: if 1 = s 3 00172: then go to 0263 00173: 0 -> s 1 00174: CRC 300 00175: if 1 = s 3 00176: then go to 0204 00177: if 0 … Continue reading The HP67 Keypress Wait Loop<\/span>