Service module (SM1C) and peripherial flags

[brouhaha]

(05-27-2024 08:46 AM)ThomasF Wrote:  Apparently it loads a flag pattern in the C register, and then checks to see if the FI flags are set accordingly.
But I can't understand how the flags are updated, IMHO only specific hardware can drive the FI lines and setting of the flags, this is not possible by just software.

Yes, that test won't work without a "flag-wired" module, which presumably loops the DATA signal (which usually presents the value of C) to the FI signal. It might be just a direct connection, though there's a small chance that they might have buffered it.

I brought this up once before here, and people didn't seem to believe me. The flag-wired module is mentioned in the service manuals, e.g. in the original 41C Service Manual, Table 4-1 on page 4-1, item ET-11967 "Flag-Wired Memory Module", diagnostic test table step 1 Preparation on page 4-2, and and step 12 on page 4-4, step 1 in table 4-2 on page 4-6, step 12 on page 4-11, and aslo in the Service Note 41C-35 page 3 which is generally found appended to scans of the 41C/CV/CX service manual. (For the 41CV and 41CX it would have to ba a flag-only wired module, and no P/N is given, as compared to the flag-wired-memory module for the 41C.)

Diego says that the ET-11967 is a double memory module, hard-addressed, with the flag wiring, but he apparently didn't speciificallly investigate the flag wiring. Perhaps I didn't read closely enough, but I don't recall anything in the service manual suggested to me that it had to be a double mem.