EPROM PROGRAMMER / CHECKER / READER
by C. Bowden
The equipment described in this article is the third EPROM programmer that the
author has built in the last couple of years. The first version, which was built about
two years ago, worked via the serial interface and was very slow and unreliable. It
took over an hour to ‘burn’ a 2708.
Version number 2, built about a year ago, worked through the Nascom PIO and
was much faster, taking only a couple of minutes for the same task. It was also much
more reliable, and the software included routines to copy EPROMS to RAM, and to
verify them against RAM. One disadvantage, however, was that it would only
program 2708 EPROMS, although the basic hardware was suitable for extension to
2K EPROMS, such as the 2716/2516.
The third version, described in this article will work with 2708, 2516 and 2716
EPROMS, and some of the routines can also be used with mask-programmed ROMS
which are pin-compatible with 2716s, such as the ROMS used in the NASCOM 2 for
Nas-Sys and Graphics. Two extra routines have been added, and the unit will now
carry out the following tasks:
- Check whether the EPROM is erased, and display a suitable message.
- Program the EPROM from data in RAM, and display a progress count.
2708/2516/2716 EPROMs, and pin compatible ROMS
- Transfer the contents of the chip into RAM at a chosen address.
- Compare the contents of the chip against RAM, and display errors.
- Dump a copy of the chip contents to a printer on the serial port,
displaying memory locations and hex and ASCII data.
The program occupies about 2K bytes of memory space. No attempt has been
made to reduce this for the following reasons:
- The program has been written so as to minimise the chance of
operator error, by offering single-key choices backed up by verification
of entry wherever possible. This requires a large number of messages
and prompts, which take up a lot of memory space.
- Because of this, it would have been difficult to keep the size of the
program below 1K bytes; 2K seemed to be suitable, as the program
would then fit into a ‘self-programmed’ EPROM.