====== IO Board ======
16 Bit Digital input, 16 Bit Digital Output.

{{:projects:electronics:ioboard:io_board.jpg?600|}}


===== Outputs =====

16 Relays


====== Inputs ======
{{:projects:electronics:ioboard:hp3700.png?300|HP3700}}

16 socketed Optoisolators, rated for 5 to 240 Volts, AC or DC.


====== Pinout ======

^Relay board^Signal Name^Pin^#^Pin^Signal Name^
||Gnd|Ground |B1 ^#|A1 |-I/O CH CK|I/O channel check; active low=parity error|
|A3,B3 on U21|RESET DRV |B2 ^#|A2 |SD7 |A1 on U24|
|+5V|+5 V dc |B3 ^#|A3 |SD6 |A2 on U24|
|n/c|IRQ 9 |B4 ^#|A4 |SD5 |A3 on U24|
|n/c|-5 V dc |B5 ^#|A5 |SD4 |A4 on U24|
|n/c|DRQ2 |B6 ^#|A6 |SD3 |A5 on U24|
|n/c|-12 V dc |B7 ^#|A7 |SD2 |A6 on U24|
|n/c|-0WS |B8 ^#|A8 |SD1 |A7 on U24|
|Connected|+12 V dc |B9 ^#|A9 |SD0 |A8 on U24|
|Gnd|Ground |B10^#|A10|I/O CH RDY|n/c|
|B2 on U23 - not used|-SMEMW |B11^#|A11|AEN |Address enable; active high when DMA controls bus|
|B1 on U23 - not used|-SMEMR |B12^#|A12|SA19 |n/c|
|A3 on U23|-IOW |B13^#|A13|SA18 |n/c|
|A4 on U23|-IOR |B14^#|A14|SA17 |n/c|
|n/c|-DACK3 |B15^#|A15|SA16 |n/c|
|n/c|DRQ3 |B16^#|A16|SA15 |n/c|
|n/c|-DACK1 |B17^#|A17|SA14 |n/c|
|n/c|DRQ1 |B18^#|A18|SA13 |n/c|
|n/c|-REFRESH |B19^#|A19|SA12 |n/c|
|n/c|CLK |B20^#|A20|SA11 |n/c|
|n/c|IRQ7 |B21^#|A21|SA10 |n/c|
|n/c|IRQ6 |B22^#|A22|SA9 |A1 on U23|
|n/c|IRQ5 |B23^#|A23|SA8 |A2 on U23|
|n/c|IRQ4 |B24^#|A24|SA7 |B4 on U22|
|n/c|IRQ3 |B25^#|A25|SA6 |B3 on U22|
|n/c|-DACK2 |B26^#|A26|SA5 |B2 on U22|
|n/c|TC |B27^#|A27|SA4 |B1 on U22|
|n/c|BALE |B28^#|A28|SA3 |A4 on U22|
|+5V|+5 V dc |B29^#|A29|SA2 |A3 on U22|
|n/c|OSC |B30^#|A30|SA1 |A2 on U22|
|Gnd|Ground |B31^#|A31|SA0 |A1 on U22|

====== IC's ======

^Label^Chip^Count^Description^
| |HP3700|16|Opto-isolator|
| |ULN2803A|2|driver|
|U27|74HC374|1|IP/FLOP OCTAL D-TYPE|
|U17,U28,U35|HC373|3|LATCH OCTAL 3ST D|
|U16|HC374|1|FLIP FLOP OCT 3ST|
|U20|HC138A|1|IC DECODER 3-TO-8 LINE|
|U39|HC688|1|IC COMPARATOR EQUALITY 8B|
|U22,U23|HCT244A|2|IC BUFF/DVR TRI-ST DUAL|
|U21|HC00A|1|IC GATE NAND QUAD 2INP|
|U19|HC32A|1|IC GATE OR QUAD 2INP|
|U38|74HC74AM|1|F/F W/CLR&SET DUAL D|
|U25|74HC4538M|1|IC MULTIVIBRATOR DUAL HS|
|U24|HCT245A|1|IC TRANSCVR 8BIT N-INV|