Instruction manual

Essex Electronics, Inc. | 805.684.7601 | 800.KEY-LESS | fax [phone] | keyless.com
20
ABA Track II Clock & Data Reader
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! ABA Track II Specifications
GREEN <Clock> goes low to clock in data. WHITE <Data> output
is determined by ORANGE. If ORANGE is low, then Data output is
inverted. If ORANGE is high, then Data output is normal.
Clock and Data signals are open collector outputs with 2.2K pull-
ups to the internal +5v. Clock Pulse is sent at 200 usec. Interbit
delay is 750 usec. An annunciator beeps with each key press. An
output is generated with each key press which can be used to
drive a CCTV or Security Light. Located through the BLUE wire
(see Connector Wiring), this is an open collector output capable of
sinking 1/4 A with a 30 second on time.
Each key press generates an ABA Data Format as follows:
1. Each character is sent as a 5 bit value. The first 4 bits of each
character are the data value LSB first. The last bit of each
character is an odd parity bit. The first four 0’s are sent as lead
in.
2. The Start Character is sent next. The Start Character is a “B”
with odd parity bit. Each entered character is now sent as 5
bits per character with odd parity and LSB first. There can be
up to a max of 12 characters.
3. After all the keyed in characters have been sent, then the End
Sentinel is sent. The End Sentinel is an “F” with odd parity.
Next the LRC code is sent as a 5 bit character with odd parity.
The LRC code is created by XORing all of the characters sent
including the Start Characters, the Digit Characters and the
End Sentinel. It is calculated as a 4 bit value from XORing all
the previous characters. Its value is then sent as a 5 bit value,
the 5th bit being its own odd parity.