HP-71b CMT-64E Eprom - Whats under the black goop ?

[KimH]

About a cleared EPROM disturbing the 71B

I just erased 2 64kb front port EPROM modules from CMT.

I wanted to see if the erase was completed properly. Placed them in Port 3 & 4

PEEK as provided in the 71B OS ROM won't PEEK as the EPROM is seen as a protected ROM. [ERR:File Protect]

SYSEDIT from the JPC E2 was my friend, found the ROMs and they were all "F".

ROMs seem to be placed underneath the Card Reader area sort of Top Down regardless of which port they go into.

I suspect - as J-F suggests - that the cleared ROMs would disturb the machine, so I removed them once done checking.

& J-F: Thanks for sharing that the 32k EPROMs for HHP are complemented! Programming one of those is my next project - when it rains again...

(03-18-2020 08:29 AM)J-F Garnier Wrote:  

(03-18-2020 05:48 AM)Dave Frederickson Wrote:  On p.4 of the document is a picture of an HHP card reader port EPROM module. How was this module programmed?

I did program HHP card-reader EPROM module back at the time, some for professional applications. The EPROM was programmed on a standard EPROM programmer, the only thing to know is that the bytes are complemented, I guess to make an erased EPROM (all FF) looks as zero bytes from the HP71. This is not true for CMT front port EPROM module, an erased module disturbs the HP71 operations.

J-F