A simple 8039 controller design

by Ed, http://www.alphalink.net.au

This is a design for a simple 8039 based microcontroller.
Included are schematics, pcb layouts and Protel DOS files.

Any microprocessor in the 8048 family may be used. These

	8035, 8039, 8040	external rom
	8048, 8049		internal rom
	8748, 8749		eprom

In this design the internal program memory of the 804x
and 874x chips are disabled - program instructions will
be supplied by the external eprom.

Links on the board allow for any eprom from 2716 to 27256
to be used. (It should be noted the 8048 family may only
address a maximum of 4k bytes of program memory, however).

If one of the larger eproms is used (2764 or above) then
link JP3 allows eprom memory in the range 1000h-1FFFh to
be re-mapped to 0000h-0FFFh. This can be handy during
program debugging - you get two chances of getting your
program right before you need to erase the eprom and try

A 20 pin IDC header brings out all the user-accessable
I/O pins via a ribbon cable. The idea is that you can
use the same micro board for any project - just plug in
a different I/O card!

The onboard power supply allows any voltage in the range
9 to 12 volts AC or DC to be used.

PCB layouts have been included for those having the
means to make one. The PCB can be made single or
double-sided. If single-sided is chosen, use wire links
on the top of the board as shown in the 'top layer'

An etched PCB is not essential, however. I have had
good success simply using wire-wrap pcb board, standard
dual-wipe IC sockets and simply solder point-to-point
with wire-wrap wire.

Any crystal in the range 2 to 12 MHz may be used but
check the specifications of the microprocessor you will
be using. (Some brands of 8039 require a minimum 6 MHz
clock while 6MHz is the maximum for most 8748/49's.)

The schematic and PCB files were produced using Protel
DOS based software (Schematic and Autotrax).