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CHAPTER 18 IEBus CONTROLLER (V850/SC2)
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User’s Manual U15109EJ3V0UD
Cautions 1.
Even when the slave transmission enable flag (ENSLVTX) is not set (1), ACK is
always returned if slave status request control data is received.
2.
Even when slave reception enable flag (ENSLVRX) is not set (1), NACK is always
returned by the acknowledge bit in the control field if data/command writing control
data is acknowledged.
Slave reception can be disabled (communication stopped) by ENSLVRX flag only in
the case of independent communication. In the case of broadcast communication,
communication is maintained and the data request interrupt (INTIE1) or IEBus end
interrupt (INTIE2) is generated.
(c) Last acknowledge bit of telegraph length field
The last acknowledge bit of the telegraph length field serves NACK in any of the following cases, and
transmission is stopped.
•
If the parity of the telegraph length bit is incorrect
•
If a timing error occurs
(d) Last acknowledge bit of data field
The last acknowledge bit of the data field serves NACK in any of the following cases, and transmission is
stopped.
•
If the parity of the data bit is incorrect
Note
•
If a timing error occurs after the proceeding acknowledge bit has been transmitted
•
If the receive data is stored in the IEBus data register (DR) and no more data can be received
Note
Note
In this case, when the communication executed is individual communication, if the maximum
number of transmit bytes is within the value that can be transmitted in one frame, the transmission
side executes transmission of that data field again. For broadcast communication, the transmission
side does not execute transmission again, a communication error occurs on the reception side and
reception stops.
18.1.7 Transfer data
(1) Slave status
The master unit can ascertain why the slave unit did not return the acknowledge bit (ACK) by reading the slave
status.
The slave status is determined depending on the result of the last communication the slave unit has executed.
All the slave units can supply information on the slave status.
The configuration of the slave status is shown below.