TURMON and TURMONH bug

[TronDD]

Both TURMON and TURMONH Turnkey monitor ROMs have a typo/bug in them.

; THIS SUBROUTINE BUILDS 3/6 OCTAL DIGITS IN H&L
;
; SPECIAL RETURN PROVIDED BY A "SPACE", CARRY BIT SET.
; ONLY VALID OCTAL OR "SPACE" ACCEPTED. ALL OTHERS FLAGGED AND
; CONTROL RETURNS TO MONITOR.

...

FDB7 37 STC ; SET THE CARRY
FDB8 C8 RZ ; RETURN IF "SPACE"
FDB9 E6B8 ANI 0B8H ; TEST FOR VALID OCTAL

^^ This should be ANI 0F8H unless you wanted p-w to be interpreted as valid octal. :)

The TURMON PROM Manual has the program listing with the correct value.

.M000
000000 201 123
000001 272 pqr
000002 126 012
000003 254 3?
.M0
000000 123
000001 012
000002 012
?00003 254
.

[AltairClone]

Very interesting! The TURMON manuals I’ve found also have B8h (270 octal) in them. Send me a link to the manual you found with the corrected value.

Mike

[TronDD]

Nope, you're right. My brain mistranslated 270. It is B8H. So now the question is why?

Was it a typo in the manual or is that bit sometimes relevant in some way?

[AltairClone]

Either it's just a mistake that was never corrected, or MITS had some oddball in house terminal that sent 30h-37h or 70h-77h when octal digits were typed based on some shift key or something on the keyboard and they wanted it to work either way.

I think i have an original TURMON EPROM. I'll dump it soon and see if it has B8 or F8.

Mike

[TronDD]

I'm afraid it's going to end up being B8 and I'll remain confused. :D

There's a few cool tricks used in that code so I would guess they knew what they were doing.

Tim.

[AltairClone]

The original TURMON PROMs I just examined also have B8h. Actually, MITS hardware and software designs were mediocre at best. Wouldn’t be surprised if it’s an oversight.

Mike

[TronDD]

Huh... Thanks for looking. Very interesting.