Dawn CONTROL-1500A Manual page 77

CONTROL-1500A Single Axis Antenna Controller
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State 3 (Slave Data State) if received address byte equals a slave's address.
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State 1 (Slave Idle State) if received address byte does not equal a slave's address.
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State 2 (remain in current state) if STX byte is received, which may be the beginning of a new message data
block.
State 3 (Slave Data State). In State 3, a slave is engaged in receiving the command and
associated data bytes sent by a master-controller.
A slave will exit State 3 and enter:
•
State 4 (Slave Data Error State) if ETX byte is received signifying the end of data in the message.
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State 1 (Slave Idle State) if invalid command, or data character, or incorrect number of data bytes is received.
State 4 (Slave Data Error State). In State 4, a slave is waiting to receive a Checksum byte that
tests the transmitted message for errors.
A slave will exit State 4 and enter:
•
State 5 (Command Execute State) if a Checksum byte is true -received LRC value of Checksum byte equals
the LRC value computed by a slave during message reception.
•
State 1 (Slave Idle State) if a Checksum byte is false -- received LRC value of Checksum byte does not equal
the LRC value computed by a slave during message reception.
State 5 (Command Execute State). In State 5, a slave, having completed reception of a
message, executes a function specified by a command byte. A slave will send an appropriate
response message to a master-controller after receiving the last character of the message.
A slave will always exit State 5 and enter Device Idle State, State 1.
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Appendix D The RCI RS422 Interface Spec 70