User manual

Chapter 3
VMEbus Interface
3-6
Offset Register
11111111SLAVE BASE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
07
offset
The SLAVE-BASE field in the offset register defines the A24
mapping of the PLC-5/VME processor; register bits 15-8 are the values of
the VME address bits A23-A16. This field is not altered by the
PLC-5/VME processor.
Command Control Register
WRDY LOCK ERR 1
COPY-TO-STATE COPY-FR-STATE
ERROR CODE
Command Control and Lock Register
WRDY LOCK ERR 1 COPY-TO-STATE COPY-FR-STATE ERROR CODE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
09
offset
0B
The command-control register and command-control-and-lock register
contain state bits (Table 3.B) associated with the command register. They
are identical except how they read the command-control-and-lock register
and affect the state of the LOCK bit. The command-control-and-lock
register and the LOCK bit are provided to support multiple independent
senders of commands to the PLC-5/VME processor; you can ignore both
the register and the bit if you do not need this facility.
T able 3.B
Registers Containing State Bits
Bit Register Function Definition
15 WRDY Write ready If 1, the command register is armed for an incoming command.
A write to the command-low register clears this bit.
14 LOCK Command register lock If 1, the command register has been locked.
If clear, the command register can be locked for the sending of a command.
13 ERR Protocol error If 1, a protocol error occurred associated with the last command received.
11-10 COPY-TO-STATE The current state of the
continuous-copy-to-VME
operation
00 None is enabled
01 Currently enabled and no errors encountered
10 Currently enabled but a noncatastrophic error has occurred
11 Shutdown because a catastrophic error has occurred
9-8 COPY-FROM-STATE The current state of the
continuous-copy-from-
VME operation
Same encoding as above.
7-0 ERROR CODE Error code If ERR=1, this field is a code describing the error .
See specific requesting command types or Appendix D for a list of error codes.