Motorola SE955 Integration Manual page 230

Transmitting Data
The host only transmits after receiving permission from the decoder. There is no limit to the number of
characters per transmit. However, the maximum character-to-character delay cannot exceed the Host
Intercharacter Time-out parameter. The HOST RTS signal must return to inactive at the end of transmission
(unless the host wants to temporarily prevent the decoder from transmitting).
If the transmit procedure fails, the host must wait for some randomly generated time period before trying again.
Sample Code for Host Transmit Procedure
boolean host_transmit()
request permission to send
WHILE (the last character has not been sent) DO
set up serial response time out
WHILE (permission has not been granted) DO
IF (serial response time out expired) THEN
remove request to send /* transmit failed */
RETURN (FALSE) /* calling function may retry transmit */
END
END
transmit a character
END
remove request to send
RETURN (TRUE) /* transmit successful */
Receiving Data
The host must be ready to receive data from the decoder anytime the host is not transmitting. The host can
temporarily prevent the decoder from transmitting by using the Host RTS line.
Serial Interface Specification A - 5