Microbyte MZ80A-I/O CPU ASSY NO 11-1019 REV B
		=============================================
Reverse engineering notes by Lawrence Glaister VE7IT, in aid to getting this
CPU card back into service. 27 March 2021	

u1  mc1488/75188n	Quad Line EIA-232D Driver
u2  mc1489p/ds1489n	Quad Line Receivers
u3  mc1488/75188n	Quad Line EIA-232D Driver
u4  mc1489p/ds1489n	Quad Line Receivers
u5  7404		Hex Inverter
u6  sn74s74n		Dual D Flip-Flop
u7  com8116 		Standard Micro Systems dual baud rate generator
u8  24 pin zif eprom socket for 2708/2716/2732
u9  z80a 		dart dual uart
u10 am8255apc 		parallel port
u11 sn74ls04n		Hex Inverter
u12 sn74ls74an		Dual D Flip-Flop
u13 74ls266b1		Quad 2-Input Exclusive-NOR Gate
u14 sn74ls74an		Dual D Flip-Flop
u15 sn74ls00n		Quad 2-input NAND Gate
u16 74ls09b1		Quad 2-input AND Gate (Open Collector)
u17 z80a ctc 		counter timer chip
u18 z80a ctc 		counter timer chip
u19 z80a cpu 		(z8400a ps)
u20 74ls32b1		Quad 2-input OR Gate
u21 74ls09b1		Quad 2-input AND Gate (Open Collector)
u22 74ls02n		Quad 2-input NOR Gate
u23 74ls32b1		Quad 2-input OR Gate
u24 74ls09b1		Quad 2-input AND Gate (Open Collector)
u25 74ls02n		Quad 2-input NOR Gate
u26 74ls244n		Octal Driver Tri-State
u27 dm74ls125an		Quad Tri-State Buffer
u28 dm74ls125an		Quad Tri-State Buffer
u29 dm8160n 		Magnitude Comparator, 8160 Series, 6-Bit
u30 sn74ls244n		Octal Driver Tri-State
u31 sn74ls244n		Octal Driver Tri-State
u32 sn74ls244n		Octal Driver Tri-State
u33 sn74ls244n		Octal Driver Tri-State
u34 sn74ls244n		Octal Driver Tri-State
u35 sn74ls244n		Octal Driver Tri-State
u36 sn74ls240n		Octal Inverter Line Driver Tri-State
u37 sn74ls138n		3 to 8 Decoder/Demultiplexer
u38 sn74ls123n		Dual Mono Multi. With Clear

q1 2n4403		NPN General Purpose Transistor

vr1 lm323k 		5 volt regulator
vr2 l7912cv 		-12v regulator
vr3 7812c 		+12v regulator
vr4 79l06a 		-6v regulator

y1 8Mhz 		xtal processor clock *2
y2 5.0688Mhz		xtal for baud rate generator 50-19200 baud
			available in 16 steps. 2 baud clocks are at 16x 
			the baud rate set by rotary hex switches SWA SWB

J2 26 pin ribbon connecter - serial port
J3 50 pin ribbon connector - parallel port
J4 26 pin ribobn connector - serial port
J5 ??			2 unpopulated  pins

Configuration jumpers
E1 2x9 eprom selection
E2 1x3
E3 4x1
E4 1x6
E5 1x6
E6 2x4
E7 2x6
E8 2x2

E10 1x2 not populated
E11 1x2 not populated
E12 1x2 not populated

Default config jumpers - viewed with i/o connectors at the top and
S100 bus at the bottom, voltage regulators on the left.
E1
o o o o o o o o o 
| | | |
o o o o o o o o o	configured for 2708 eprom

E2
o-o o 

E3
o o o o

E4
o-o o o-o o

E5
o
|
o

o
|
o

o

o

E6
o-o
o-o
o o
o-o

E7
o o o o o o	Prom start address F800? maybe jmp start address?
| | | | |
o o o o o o

E8
o o
| |
o o


SWA hex rotary switch - serial baud rate selection E=9600 baud
SWB hex rotary switch - serial baud rate selection E=9600 baud


Chip selects/output enables for reverse engineering port/memory logic
U8 2716 eprom:  18 /ce, 20 /oe   2kx8 for onboard monitor
U9 Z80A DART: 	35 /ce, 36 /iorq  4 ports, A data, B data, A control, B control
U10 8255 PPort: 5 /rd, 6 /cs, 8 A1, 9 A2, 36 /wr 4 ports, A,B,C,Control
U17 Z80A CTC: 	6 /rd, 10 /iorq, 15 /ce, 18 cs0, 19 cs1  4 ports, chan 0..3
U18 Z80A CTC: 	6 /rd, 10 /iorq, 15 /ce, 18 cs0, 19 cs1  4 ports, chan 0..3
not sure if there are any other onboard ports used for ????