Intel 8048 - Reading the ROM for Duplication

Aloha!

I have a keyboard that uses the Intel 8048 as the keyboard encoder. There are no ROMs, PROMs or the like on the keyboard's PCB, so I have to assume that the 8048's 1K x 8 internal ROM contains the code for the encoder.

I want to duplicate this keyboard using new hardware. As part of the process, I need to read the 8048's ROM. I've never fiddled with this CPU before. I do have EPROM programmers like the TL866CS and SP300. Can I use one of these to read the 8048? Or, what reader will allow me to do this?
groinksan

Unread post13 Jul 2018, 07:08

X
groinksan
 
Posts: 16
Joined: 08 Dec 2014, 03:15
Favorite switch: Cherry
DT Pro Member: -
 
One thing I forgot to mention... I just need to read the 8048. I don't need a write solution. I intend to use an external EPROM when re-designing my keyboard design, and will program the code into it.
groinksan

Unread post13 Jul 2018, 07:34

X
groinksan
 
Posts: 16
Joined: 08 Dec 2014, 03:15
Favorite switch: Cherry
DT Pro Member: -
 
EPROM programmers normally have a device compatibility list. Have you checked?
Arakula

Unread post13 Jul 2018, 13:44

X
Arakula
 
Posts: 143
Joined: 19 Sep 2014, 10:56
Location: Austria, Europe
Main keyboard: Unicomp PC/5250
DT Pro Member: -
 
Checked both of mine - 8048 not listed in either of them. Are there other part #s for the 8048?
groinksan

Unread post13 Jul 2018, 16:38

X
groinksan
 
Posts: 16
Joined: 08 Dec 2014, 03:15
Favorite switch: Cherry
DT Pro Member: -
 
It might be listed under MCS-48 which is the family of microcontrollers or 8748 which is the programmable version of the 8048.
Engicoder

Unread post13 Jul 2018, 17:16

X
Engicoder
 
Posts: 749
Joined: 24 Oct 2012, 14:44
Location: NC, USA
DT Pro Member: 0117
 
Perhaps something like this one: https://www.ebay.com/itm/EPROM-Programm...1438.l2649

You would need a system with a parallel port though.
JP!
User avatar

Unread post13 Jul 2018, 18:12

User avatar
X
JP!
 
Posts: 906
Joined: 01 May 2017, 03:49
Location: United States
Main keyboard: Currently a Model M
Main mouse: Steel Series Sensei
Favorite switch: Beam Spring
DT Pro Member: 0194
 
The 8048 wasn't programmable; hence, it doesn't show up in compatibility lists. The ROM bits were hardwired - created by photolithography along with the other transistors on the chip.
However, the 8048 can be read. This project describes how this can be done with very little hardware (+5V plus +12V power supply, 4 MHz quarz, two 22nF, pull-up resistors). The algorithm is quite simple: pull /RESET to 0V, put the address on data bus (lower 8 bits) and port 2 (upper bits), release /RESET to +5V, which latches the address, then read the ROM byte for that address from the data bus (cf. MSC-48 User's Manual, page 2-19).
I'd suggest doing this with a teensy++, since then you can spare the inverter circuit and use its 8-bit ports for an easy interface to the 8048. (For that reason, I'm using the Teensy++ as an 8048 replacement.)
OleVoip
User avatar

Unread post13 Jul 2018, 19:35

User avatar
X
OleVoip
 
Posts: 154
Joined: 05 Feb 2015, 16:38
Location: Hamburg
Main keyboard: Tandberg
Main mouse: Wacom Pen & Touch
Favorite switch: Siemens STB 21
DT Pro Member: -
 
The Willem device looks like a winner! I'm running Windows 10 64-bit with a laptop that has a docking station/parallel printer port. I also have a Windows XP laptop with parallel port, so at worst I have the XP computer.

As for the MCS-48, neither of my programmers list that part.

The read-only project - I'll read through that, yes, I only need to read the ROM inside. The 8048 has an EA pin I can use force it to use an external EPROM.
groinksan

Unread post13 Jul 2018, 19:40

X
groinksan
 
Posts: 16
Joined: 08 Dec 2014, 03:15
Favorite switch: Cherry
DT Pro Member: -
 

Who is online

Users browsing this forum: AndyTC, Moosewing, paddle0, snot and 73 guests