Grass Valley Performer SD - Manual (Page 165)

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Serial Protocol Descriptions
A simple read of status is:
Controller: BREAK
80A0H (Poll Address)
09H (TEN character; XMIT enable)
Router: READ RESPONSE (See earlier)
Another way to accomplish the read is:
Controller: BREAK
80A0H (Poll Address)
03H (ESCAPE)
02H (# of bytes in message)
41H (READ command)
00H (Dummy data)
BDH (Checksum)
Router: 04H (ACK)
Controller: 09H (TEN character)
Router: READ RESPONSE (see earlier)
Finally, the WRITE command sequence for selecting crosspoints:
Controller: BREAK
80A0H (Address)
03H (ESCAPE)
02H (# of bytes in message)
C1H (WRITE Command)
avH (crosspoints desired a=audio 1-10, v-video 1-
10)
xxH (Checksum. 2’s complement of last 3 bytes
sum)
Router: 04H (ACK)
Protocol error is called when a protocol error occurs.
Receive error is called when a message with a bad checksum is
received.
When a READ or WRITE message is received or a STATUS
message is sent, both audio crosspoints are forced to be the same
by setting the second audio crosspoint equal to the first. Null
sources are eliminated by forcing source 1.