HP-IL RS-232 (a-may-be too-)"techie" questions.


Hi all,

To the HW gurus out there: Has someone ever got an image of the program inside the 82164A processor? (I know it's difficult but, where else could I ask?)

HP P/N:1820-3218 => Intel 8048 microcontroller, 1K ROM.

Or, does someone has an 82164A (preferebly non-working) which can be left in loan for me to extract such image? (Yes, this is even more difficult than the previous one... :-))

Thanks and best wishes from the Canary Islands.



Hi Diego,

You have a mail.

Best regards,



Although the pinout shown in the service manual does match the 8048, I think the actual part must be an 8049 or (less likely) 8050. Those are the variants of the 8048 with more memory.

The 82164 is documented as having a 109 byte receive buffer, 14 4-bit R registers, 12 bytes of C registers, and 4 status bytes. That adds up to 131 bytes, and the 8048 only has 64 bytes of RAM. Even with the 128 bytes of RAM of the 8049, it's a tight squeeze; some of the RAM is taken up by working registers and stack, so some of the 82164A R and/or C register values must be used directly rather than buffered, etc.

I doubt that it's an 8050 because that has 256 bytes of RAM, and they would have been able to make the receive buffer even larger with that part.

Be careful when reading the ROM from an 8048/8049/8050. The verify mode is similar to that of the 8748/8749 EPROM version, but the 8048/8049/8050 should have 12V on the EA pin, vs. 18V for the EPROM version. Without realizing that, I did successfully read an 8049 once on a programmer set for the 8749, but when I tried to do that with another 8049 I damaged the part.



Prabhu: Thnaks a lot, you've got mail too.

Eric: Thanks for the remarks. I was certainly aware of the electrical specs for the MSC-48 family. I haven't think of the RAM amount though, and it looks like you must be right in your assumption that the part should be an 8049, despite the designation found in the Xref. tables. Anyhow, I also have the tools to preperly (and safely) read any of the types.

I'm concerned about the need of removing the chip. Does anyone know if it's placed in a socket or just soldered on the board?

Best wishes from Spain.



The service manual doesn't indicate that the part is socketed, so it seems fairly unlikely that it would be.

What equipment do you use for reading the masked-ROM parts? I've got a bunch of different commercial EPROM programmers, and all of them handle the EPROM parts but none of them handle the masked-ROM parts.

The last time I did this I hand-wired an adapter that disconnected pins 7, 25, and 26, wired pin 26 of the chip to pin 40 of the socket (Vcc), and had a 7812 regulator taking the 25V from pin 26 of the socket and providing 12V to pin 7 of the chip. This adapter worked on some programmers but not others, possibly due to the sequencing of the reset signal and Vpp by the programmer.


I have the FSI164A which is almost identical in operation and instructions but has bigger buffers and more RS-232 channels (2 standard and up to 8 was optional) and had a battery option. It has an EPROM which I refreshed just a few years ago so I could catch it before the data went bad since it was about 20 years old. I thought I kept a .hex file of it I could email you but I can't find it at the moment and have not gotten my old Needham's EPROM programmer going again since changing DOS computers. I'm sure I just have to change the I/O address which is at 300h at the moment.



I'm using a Willem programmer, with some mods on my own, and the corresponding MSC-48 adapter.

It handles the whole family: ROM (8048, 8049, 8050), OTP and EPROM (8748, 8749).

It's a convenient device which also programs a wide range of EPROM's EEPROMs, Flash, Dallas (RTC's)... and serial devices: PIC's, I2C, SPI, Microwire...

Only drawback is that you need a parallel port (farily scarcy nowadays) to connect it to your computer.

Best wishes.


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