HP Portable Plus - ROMBO 128 KB EPROMS?

[Martin Hepperle]

While playing with my Portable Plus and reading many issues of the Portable Paper I became interested in burning EPROMS larger then 64 KByte.

In those days, Hal Goldstein offered the ROMBO EPROM burner and special 128 KB EPROM modules, consisting of a thin PCB with DIP-28 pins and a 32-pin EPROM with 128 KB.
Somewhat similar to what was available for HP-41 and 71 calculators.

Does one of you of you have such an EPROM module and could take some pictures?
I would especially be interested in the pinout/connections of this 28 to 32 adapter.
Maybe it is possible to create a clone of it.

Thank you for looking,
Martin

[Dave Frederickson]

(07-19-2020 08:34 AM)Martin Hepperle Wrote:  I would especially be interested in the pinout/connections of this 28 to 32 adapter.

This wouldn't be hard to reproduce. The ROM pinout is on Technical Reference Manual p. K-4 and the pinout for a 128k 32-pin DIP is readily available. A 4-pin adapter will be needed to connect the additional pins to the programmer and the module will need a header for the additional signals along with a couple of jumpers to switch A16, A15, and VPP.

As far as programming, VGER can generate two 64k odd/even images that could be shuffled together to make the 128k bin file.

Dave

[Martin Hepperle]

I figured that I only need these connections:

Code:

from       to
socket    EPROM    
  22         2      former OE/ to A16 (with jumpers (A) this is A16 from the CPU bus)
  28        32     VCC to VCC (rerouted)
 GND        24    new OE/, always enabled

additional new pins

Code:

VPP    1   n.c. or ground?
P/    31   n.c. or VCC?

The jumpers (A) and (B) control how the address lines A15 ad A16 are connected to the ROM/EPROMs. All in position (A) direct A15 and A16 to the socket pins A15 resp. OE/.
This is the same setting as used for the 64 KByte EPROMs.
I have to evaluate whether a 27C1001 on a PCB still fits the space before resorting to some PLCC chip. Maybe for starting some lifted pins and flying wires are o.k., but not nice for repeated EPROM programming.

Chip pinouts:

Code:


   64 KByte                       128 KByte
                               VPP    1    32    VCC
                               A16    2    31    P/
A15    1    28    VCC          A15    3    30    n.c.?
A12    2    27    A14          A12    4    29    A14
A7     3    26    A13          A7     5    28    A13
A6     4    25    A8           A6     6    27    A8
A5     5    24    A9           A5     7    26    A9
A4     6    23    A11          A4     8    25    A11
A3     7    22    OE/, VPP     A3     9    24    OE/
A2     8    21    A10          A2    10    23    A10
A1     9    20    CE/          A1    11    22    CE/
A0    10    19    Q7           A0    12    21    Q7
Q0    11    18    Q6           Q0    13    20    Q6
Q1    12    17    Q5           Q1    14    19    Q5
Q2    13    16    Q4           Q2    15    18    Q4
VSS   14    15    Q3           VSS   16    17    Q3

[Brian Hudson]

I own a ROMBO EPROM programmer from Personalized Software. I have the manual and some custom 128KB EPROM modules, but I lost the software. I contacted Hal Goldstein, but he was unable to find a copy in his archives. I bought a generic USB programmer that I will use to duplicate some 27C512 (64KB) EPROMs. I will also try to duplicate some 128KB ROMs onto the custom 128KB EPROMS. 27C1024 (128KB) EPROMS are 32-pin packages, so the Personalized Software custom EPROM module mounts a 32-pin PLCC package on a PCB adapter to 28 pins. To program on the ROMBO, two jumpers are removed from the module, and a 5-pin cable connects the jumper pins to a personality module on the ROMBO. This allows ROMBO to select the upper and lower 64KB blocks during programming.

Portable Plus reads software drawer ROMs as 16-bits wide, whether the ROMs are singles or pairs. Singles are programmed byte sequential, but pairs are programmed even bytes in first ROM and odd bytes in second ROM. ROMBO software included an interleaving utility for user-generated DOS source files.

I have sharp photo of the 128KB modules.

[Martin Hepperle]

... in the meantime ... I created an external EPROM interface for the 128 KB EPROMs and indeed it works as a halfbank filled with Turbo-C executables. Next experiment will be a fullbank 256 KB package spread over 2 chips.

Small UV-erasable EPROMS in the PLCC-32 case seem to be unobtainable, so one would probabaly have to switch to a similar Flash ROM for a smaller package.

Martin

[attachment=9987]

[attachment=9988]

[Dave Frederickson]

Since the chip will need to be upgraded, consider using a larger size device and coming up with a method to bank-switch images using a few jumpers.