|Description (may be empty)|
|1||CH-REQH||Request output to changer; Low : Request|
|4||CH-CON||Changer control out; High : Operation mode Low : Standby|
|5||CH-MUTE||Mute request from changer; High : Mute|
|7||CH-RST||Reset output to changer|
|8||R||Audio right channel|
|9||CH-REQC||Request input from changer; Active Low|
|10||CH-DATAC||Data input from changer|
|11||CH-DATAH||Data output to changer|
|12||L||Audio left channel|
|13||CH_CLK||Clock input/output for changer|
Pins 5,8,9,10,12 - for input, pins 1,4,7,11 - for output, pin 13 - input/output.
When the transfer is started by the radio by setting its REQ line (CH-REQH) low it waits for the changer to do the same on its REQ line (CH-REQC) and then sends the 4 byte address header, the data size in bytes and then the data.
The changer can start the communication by lowering its REQ line. The radio will send 4 address bytes and 1 data size byte (which is 40 clock cycles). The radio will set its REQ line low if it accepts the transfer.
A clock rate is 125 KHz. The data is transfered in bytes (8 bits with MSB first) and is valid at the rising clock edge.