Omen Alpha Guide

OMEN ALPHA
=========
OMEN Computers - - - https://github.com/osmibity - - - Page: 1
OMEN Alpha / issue 4
Technical Documentation

OMEN ALPHA
=========
OMEN Computers - - - https://github.com/osmibity - - - Page: 2
INTRODUCTION
===========
The OMEN Alpha computer kit is a low-cost computer trainer, based on the Intel
80C85 CPU. It has these features:
-80C85 CPU working at 1.8432 MHz
-32 kB RAM
-32 kB EEPROM
-Serial port up to 115.200 Bd / MC6850
-3 parallel ports / Intel 8255
-Application system bus

OMEN ALPHA
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OMEN Computers - - - https://github.com/osmibity - - - Page: 3
ASSEMBLY INSTRUCTIONS
===================
1. Solder sockets for the integrated circuits
2. Test all soldered connections
a. Test if all pins are well connected
b. Check if GND is not short connected to Vcc
c. Check if each IC has properly connected GND and Vcc
3. Solder all passive parts /capacitors, diode, resistors, push button,
crystal/
4. Connect the power adapter and check
5. Insert the CPU into its socket /keep the proper orientation!/ and try to
power it up. Check if oscillator lives /at CPU pin 37/
6. Insert the essential ICs: 74245, 74573, 7400, 62256 and AT28C256. Again:
keep the proper orientation! Bad orientation can damage the IC!
7. Connect the serial pins TxD, RxD and GND /pinhead JP1/ to the TTL-to-
USB converter
8. Start the serial terminal on your PC, select proper serial port and set
the parameters to 115.200 Bd, 8 data bits, no parity, 1 stop bit.
9. Power your Alpha and check the terminal.

OMEN ALPHA
=========
OMEN Computers - - - https://github.com/osmibity - - - Page: 4
MONITOR
=======
The main software for OMEN Alpha issue 4 is the Dave Dunfield’s MON85 Serial
Monitor, improved by Roman Borik.
Usage is described on the https://8bt.cz/mon85 or see the Appendix 1
You can invoke the installed Tiny BASIC v.2 by jumping to the 1000h –just
enter “G1000” /no quotes/ and press the ENTER key.

OMEN ALPHA
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OMEN Computers - - - https://github.com/osmibity - - - Page: 5
THE BOARD
========
Jumpers and pin headers
--------------------
JP1: Serial port. Pins are GND, TxD, RxD from left to right, RxD is next to the
JP1 label
JP2, JP3, JP4: Parallel ports. See below. The square marks the pin 1.
JP5: EEPROM write enable. Short pins 1-2 to disable writing, or short pins 2-3
to enable writings. Pin 1 is on the left, pin 3 is next to the JP5 label
JP7: RST7.5 enabler. Close to disable interrupts, open to leave it on the
application bus. Connect the 10k resistor to make it “open-collector signal”.
JP8: Serial signals SID and SOD

OMEN ALPHA
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OMEN Computers - - - https://github.com/osmibity - - - Page: 6
PARALLEL PORTS
=============
JP2:
+-----+-----+-----+-----+-----+
| GND | PA7 | PA6 | PA5 | PA4 |
+-----+-----+-----+-----+-----+
| Vcc | PA0 | PA1 | PA2 | PA3 |
+-----+-----+-----+-----+-----+
JP3:
+-----+-----+-----+-----+-----+
| GND | PB7 | PB6 | PB5 | PB4 |
+-----+-----+-----+-----+-----+
| Vcc | PB0 | PB1 | PB2 | PB3 |
+-----+-----+-----+-----+-----+
JP4:
+-----+-----+-----+-----+-----+
| GND | PC7 | PC6 | PC5 | PC4 |
+-----+-----+-----+-----+-----+
| Vcc | PC0 | PC1 | PC2 | PC3 |
+-----+-----+-----+-----+-----+

OMEN ALPHA
=========
OMEN Computers - - - https://github.com/osmibity - - - Page: 7
SYSTEM APPLICATION CONNECTOR
=========================
This connector is on the upper edge of board. Pin 1 is on the left side.
Pins:
1/WR
2D0
3D1
4D2
5D3
6D4
7D5
8D6
9D7
10 A0
11 A1
12 A2
13 /RD
14 IO1 --- 20h –27h
15 IO2 --- 10h –17h
16 IO3 --- 30h –37h
17 IO4 --- 08h –0Fh IOx signals are decoded by 74138
18 IO5 --- 28h –2Fh
19 IO6 --- 18h –1Fh
20 IO7 --- 38h –3Fh
21 Vcc
22 GND
23 RST7.5 -- see JP7
24 CLK
25 RESET -- Output signal
26 READY -- Pull it low to force a WAIT state
27 /BUSRQ /not connected on Alpha/
28 /BUSACK /not connected on Alpha/
29 /not connected on Alpha/
30 /not connected on Alpha/

OMEN ALPHA
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OMEN Computers - - - https://github.com/osmibity - - - Page: 8

OMEN ALPHA
=========
OMEN Computers - - - https://github.com/osmibity - - - Page: 9
PERIPHERAL IC ADDRESSES
=====================
ACIA 6850:
--------
DEh –Controll Register / Status Register
DFh –Data Register
PPI 8255:
-------
04h –PORT A
05h –PORT B
06h –PORT C
07h –Control port

OMEN ALPHA
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OMEN Computers - - - https://github.com/osmibity - - - Page: 10
MEMORY MAP
==========
0000h –7FFFh - EEPROM 32k
8000h –FFFFh –System RAM