Grass Valley Performer SD - Manual (Page 164)

3-46
Section 3 — Operation & Service
All valid addresses are in the form 8xx0 (select)/8XX1 (poll),
where xx is the address determined by switchS1. This allows
control of up to 256 serially interfaced devices on the same RS422
bus.
SMPTE protocol requires 8 data bits plus an EVEN parity bit, plus
ONE stop bit. Parity is set using internal switches as described in
the Installation section of this manual.Use of the TEN–XL READ
command is included only for historical reasons. It is simpler just
to send TEN (09H) when in the SELECT state. In the following
examples, assume the router address is set to 0AH, resulting in a
SMPTE select address of 80A0H.
Polling is as follows:
Controller: BREAK
80A0H (Poll Address)
Router: 0XH (single byte; see below.)
The following four bytes are valid responses to a poll (listed in
order of priority):
RST (07H): Power up or other reset since last poll.
NAK (05H): Time-out, parity, or invalid command error.
SVC (08H): Change in status since last poll.
ACK (04H): No change in status since last poll.
The router crosspoint and power supply status message (READ
RESPONSE) has the following structure:
Byte 1 = 03H (ESC character)
Byte 2 = 03H (# of bytes in message itself)
Byte 3 = C1H (command code for WRITE)
Byte 4 = avH (crosspoint status, a=audio 1-10, v-video 1-10)
Byte 5 = 00H (power supply status, see below 1 )
Byte 6 = xxH (checksum; 2’s complement of the sum of
Bytes 2, 3, 4, 5)
1. Performer does not use this message; supplies assumed OK.