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

Part Number KBDSER132

DC Electrical Characteristics

Symbol

Description

Min

Typical

Max

Units

Notes

Supply Voltage

2.4

5.25

V

Supply Current

2

8

mA

High Output Level

V

Low Output Voltage

0.75

V

Input High Level

2.1

V

Input Low Level

0.8

V

High Level Source Current

10

mA

Low Level Sink Current

25

mA

Capacitive load

3.5

10

pF

Input leakage

1

nA

Pull Up Resistors On Row Inputs

4

5.6

8

k?

Theory Of Operation

The KBDSER132 IC is a custom programmed microprocessor designed to encode keyboards

and provide a serial output. The open drain COL X pins are pulsed low one at a time, and the

ROW Y pins are sampled to check for key switch closures. If a key is detected, scanning stops

until the key is released. The pressed key is encoded and transmitted in standard asynchronous

format on the SOUT key. The key is transmitted using 8 data bits, 1 stop bit and no parity. Baud

rate is 9600 BPS. When the key is released scanning continues. A program such as

REALTERM may be used to view the binary data as hexadecimal. Hyperterm will not show data

in hexadecimal format.