Rane SR 4 - Manual (Page 18)

Manual-18
SR 4 Communication Protocol
The SR 4 communication protocol follows Rane’s RW 485 specification. The follow-
ing describes the SR 4 implementation.
Physical
The baud rate is 38,400 bps with No parity, 8 Data Bits, 1 Stop Bit (N81) format. The
SR 4 also supports 9600, 19200, 57600, and 115200 bps. When configuring Remotes
used with Rane controllers (RPM 22, 44, 88), the RW 485 baud rate of 38400 bps is
required. At the end of a command message, the Master must release the bus within
10 ms. The SR 4 waits this length of time before transmitting its response. To restore
the SR 4 communication settings to 38400 baud 10 ms delay, apply power while
pushing the encoder in for several seconds until the encoder LED illuminates.
Master/Slave
RW 485 is a master/slave bus network, with only one master in charge, which we de-
fine as the Protocol Master (controller). When the Protocol Master expects a response
from a slave, it relinquishes control of the bus, allowing the slave to drive the RS-485
bus.
The slave must then release the bus back to the Protocol Master, and we start again.
The SR 4 is always a slave.
Value Encoding
All numeric values are represented in ASCII decimal format separated by commas.
Values with the MSB set ($80 or larger) are interpreted as potential device addresses.
Syntax
Command messages are sent from the Protocol Master to the SR 4. Response mes-
sages are returned to the Protocol Master from the SR 4. The SR 4 always responds to
the Protocol Master upon receiving a complete command message at the correct baud
rate.
Command and response messages have the same format:
message =
<addr> Each device has a unique address in the range [0, 7]. The encoding is one
byte with the MSB set.
For example, if the SR 4’s address switch is set to 5, the controller would send
10000101. ($5 + $80)
The SR 4 always returns its address switch setting plus $80. ($addr + $80)
The address switch must be set in the range [0, 7].