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HP Portable Plus - ROMBO 128 KB EPROMS?
07-19-2020, 08:34 AM (This post was last modified: 07-19-2020 08:35 AM by Martin Hepperle.)
Post: #1
HP Portable Plus - ROMBO 128 KB EPROMS?
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
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07-19-2020, 04:54 PM
Post: #2
RE: HP Portable Plus - ROMBO 128 KB EPROMS?
(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
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07-20-2020, 07:28 AM (This post was last modified: 07-20-2020 07:29 AM by Martin Hepperle.)
Post: #3
RE: HP Portable Plus - ROMBO 128 KB EPROMS?
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 addess 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
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