Grass Valley XSwitch Feb 08 2006 - Manual (Page 32)

32 XSWITCH Installation and Operation Manual
Appendix A — Remote Activation
Command and reply packets are organized similarly, the only difference
being that reply packets do not have a Command/Control field. Packets
are ordered as follows:
Note When using the Basic Protocol, the two CRC bytes are not used.
• DEST: Destination Address field (1 word). Range: 0-255 binary. This is
the address of the device to which packet is being sent. Address 255 is
a Broadcast address. Broadcast packets are received by all devices, but
no reply is sent. (Default Address 0)
• SRC: Source Address field (1 word). Range: 0-254 binary. This is the
address of the device from which the packet is being sent. (Default
Address 255)
• LEN: Length of data field (1 word). Range: 1-256 (0=255) binary. The
packet data field includes words following the length word up to, but
not including, the CRC field
• C/C: Command/Control field (1 or more words). Command codes are
ASCII numbers ranging from 0 to 255. Control codes are binary
numbers ranging from 0 to 47
• DATA: Data field (0 or more words). The data field can be empty, or
contain either ASCII or binary words. If the data is ASCII, then, in the
case of a command packet, data is separated by a colon(:). Binary data
has no explicit separator. (see particular device command list for
further information)
• CRCL: Lower half of cyclic redundancy check (1 word). The CRC com-
putes using the CRC-CCITT polynomial
• CRCH: Higher half of cyclic redundancy check (1 word).
Error recovery is handled by the originating device. This device may
choose to terminate or re-transmit the command.
Note All bus communications are half-duplex.
Universal Command Control Codes
0.... Send device ID and firmware version number.
Example reply:
15:1.0 (ID code = 15, firmware = 1.0)
0,1. Send copyright message.
0 1 2 LEN+3 LEN+4 LEN+5
DEST SRC LEN C/C DATA1 ... DATAn CRCL CRCH