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ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104

Part Number SIOA7

Copyright © 2014 ABCircuits. Revised September 2014 Page 9 of 10

Low Level Sink Current

25

mA

Capacitive load

3.5

10

pF

Input leakage

1

nA

Pull Up Resistors On Inputs

IA0-6

4

5.6

8

k?

Note 1: Vdd=5VDC, all inputs and outputs open

Theory Of Operation

The SIOA7 IC is a custom programmed microprocessor designed to monitor and control a serial

input and output stream.

When a byte is received on the SIN- pin, bit 8 is checked. If bit 8 is 1 and bits 7,6, and 5 are 0 the

lower 4 bits are compared to the ADR0-3 pins. If that also matches, the next byte received on the

SIN- pin is placed on the OA0-6 pins if the eighth bit is zero. After the data is placed on the OA0-

6 pins, the RXP pin generates a positive pulse. Next the bits from IA0-6 are transmitted on the

SOUT- pin. Bit 8 is transmitted as a zero. The RXE pin is set high before the start bit, and set

back low after the stop bit of the transmitted byte.

The data is standard asynchronous format 8 data bits, 1 stop bit and no parity. Baud rate is 9600

BPS. It is recommended that the address byte and the OA0-6 byte be sent periodically even if

there is no change, to recover from power failure or serial data errors.