HP 71B Diagnostic ROM

[Reinhard Hawel]

Hi Guys,

You could separate the memory module(s) into Ports and check them module by module. The 71B contains four memory "modules" (in fact the internal memory consists of some small RAM zone plus four chips identical to a memory module.
Separating these modules into ports will keep your machine alive without lock up when you run programs. The small 1.5k portion has to be tested separately (and very careful while a program is running). I'm sure, when you can execute even small BASIC programs this is a sufficient test for the 1.5k. You could DIM an ARRAY and fill it with numbers or strings and read that back. Unfortunately this is far from exact for a memory test.

How to test a port:


100 COPY FILE1 TO PORT(0.01) ! 0.01 is only an example. Execute SHOW PORT for more locations
110 A = IP(ADDR$("FILE1")/256)*256 ! Beginning of the Module
120 P1$ = "AAAAAAAAAAAAAAAA" ! Test Pattern 1 16 Times 1010b
130 P2$ = "5555555555555555" ! Test Pattern 2 16 Times 0101b
140 FOR I = 1 to 256 * 2 ! 511 times 16 nibbles, first 16 nibbles not tested
150 A$ = DTH$ ( A + I * 16 ) ! Start Address as string
160 POKE (A$, P1$) ! Poke Test Pattern 1
170 T1$ = PEEK$ ( A$, 16) ! Read memory
180 POKE (A$, P1$) ! Poke Test Pattern 2
190 T2$ = PEEK$ ( A$, 16) ! Read memory
200 IF T1$ # P1S OR T2$ # P2$ THEN DISP "Mem fail at"; A$ @ I = 256 * 2
210 NEXT I

FILE1 stands for an arbitrary file name. Take any file you like.
I do not check the first 16 nibbles in line 140 because I believe, that there is some sensitive data for the file chain in the port. I think POKEing there is forbidden, but I'm not sure about that, because I write these lines without an 71B around me and no way to test it now. So please apologize my bad 71B BASIC. After all, I worked with this machine 30 - 20 years ago and this might be my first HP71B BASIC program after 10 years.
Besides that, I'm aware of the fact, that this is a really poor way of memory testing, but it's 99% sufficient and easy to write.

I'd be glad about comments

Reinhard