The HP67 card reader contains two instructions that control a “default functions” flag.<\/p>\n
The card reader integrated circuit is a Mostek MK6250N. That connects to the Arithmetic, Control and Timing (ACT) chip and actions a number of instructions that the ACT doesn’t understand. Instructions are 10 bits long. For this article the ones we are interested in are:<\/p>\n
01000 = Set the Default Functions flag, and
\n01100 = Test the Default Functions flag.<\/p>\n
The Default Functions flag controls what happens when you press the [A] through [E] keys. If it is set then [A] through [E] do the default functions ([A]=1\/x, [B]=sqrt(x), [C]=y^x, [D]=R dn, [E]=x<->y). If it is clear then [A] through [E] run user-created subroutines that start with “f LBL A” through “f LBL E”.<\/p>\n
Loading a magnetic card clears the flag. Interestingly, this is the case even if you’ve loaded a data card and there are no user-created subroutines at all.<\/p>\n
The 01000 (set-dflt) instruction appears in the HP67 roms as follows:<\/p>\n
01013: CRC 1000
\n; this seems to be initialization. it is amongst a lot of “clear data registers”
\n; and setting defaults (angle, FIX, DSP 2) in register s14 (internal)<\/p>\n
01065: CRC 1000
\n; this is probably in CL PRGM
\n; as it includes code (load constant 2; jsb 01047) to clear prog 001-112
\n; and code (load constant 1; jsb 01047) to clear prog 113-224<\/p>\n
01700: CRC 1000
\n; this happens after test\/clearing the flag if it was set
\n; see below
\n01670: 0 -> s 3
\n01671: CRC 1100
\n01672: if 1 = s 3
\n01673: then go to 01676
\n…
\n01676: load constant 4
\n01677: p <- 1
\n01700: CRC 1000<\/p>\n
The 01100 (test-dflt) instruction sets s 3 if the Default Functions flag was set. The instruction also clears the flag after testing it. It appears as follows:<\/p>\n
00344: CRC 1100
\n; appears to be just clearing it
\n; perhaps if there are program steps<\/p>\n
01671: CRC 1100
\n; as above: test, if was set then set it again<\/p>\n
13665: CRC 1100
\n; clear it<\/p>\n","protected":false},"excerpt":{"rendered":"
The HP67 card reader contains two instructions that control a “default functions” flag. The card reader integrated circuit is a Mostek MK6250N. That connects to the Arithmetic, Control and Timing (ACT) chip and actions a number of instructions that the ACT doesn’t understand. Instructions are 10 bits long. For this article the ones we are … Continue reading HP67 Card Reader – Default Functions<\/span>