AUDIOACCESS CONDI
Service Manual

AUDIOACCESS CONSUMER DIGITAL INTERFACE� DEALER DOCUMENT
Revised 4/4/96

What is CONDI� and how does it work?
CONDI� is a communications protocol developed by Audioaccess for the purpose of controlling audio and video equipment. It is based on the EIA RS-485 electrical specification and utilizes collision sensing to allow multiple devices to send and receive on the same pair of wires. Data is communicated at 9600 baud, 8 data bits, 1 stop bit, and no parity. Before beginning data transmission, the bus should be checked for inactivity. If the bus is free, transmission may commence. If the bus is being used, wait for a period of inactivity. Each transmission should be checked against the intended message, to ensure that data corruption did not occur due to multiple devices attempting to use the bus at the same time. For each valid data transmission not originating from the main controller (except Status Requests which require a different response), the main controller will automatically generate an acknowledgment (38h) (i.e. any information coming into the main controller gets an ACK). The device which sent the data should receive this acknowledgment before beginning its next data transmission. Under rare circumstances, the main controller may be performing a function which cannot be interrupted. The data should be retransmitted until an acknowledgment is received. Due to this fact, delays are required between incoming commands for the transmission of the required acknowledgment.

How does Audioaccess use CONDI� ?
Audioaccess products use the CONDI� protocol to communicate between keypads, multiple products, and the main controller. For example, whenever a button is pressed on a KPS keypad, the keypad transmits a data packet (as outlined on the following pages) to tell the main controller which button has been pressed. The keypad will continue to resend the data packet every 150 mSec until the main controller sends an acknowledge back. More specifically, whenever a button is pressed on a KPS keypad, two commands are transmitted. The first command occurs when the button is initially depressed and is referred to as the �DOWN CODE�. The main controller will respond with an �ACKNOWLEDGE� code within 150 mSec. The main controller will additionally send a �LED ON� code corresponding to the button which was depressed. The second keypad command occurs either when the button is released or when the button is depressed for more than two seconds. These two commands are referred to as the �UP CODE� and the �LONG CODE�, respectively. This is but an example of how CONDI� is used by Audioaccess products. The other types of CONDI� codes, such as Computer codes, work very similarly.

What is this document?
The first section of this document describes the structure of a CONDI� code and what each byte means. The second section demonstrates the construction of sample CONDI� codes. The subsequent sections list all of the available CONDI� codes for each device type. Appendix A contains a description of the data bytes necessary to set the MRX tuner to a desired frequency. Note: the symbols �b�, �d�, and �h� used in this document denote binary, decimal, and hexadecimal values, respectively. All transmissions must be in eight-bit hexadecimal bytes.

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