CHAPTER 19 IEBus CONTROLLER (V850/SB2)
User’s Manual U13850EJ4V0UM
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(9) Acknowledge bit
During normal communication (communication from one unit to another), an acknowledge bit is appended to
the following locations to check if the data has been correctly received.
•
End of slave address field
•
End of control field
•
End of telegraph length field
•
End of data field
The definition of the acknowledge bit is as follows:
•
0: Indicates that the transmit data is recognized (ACK).
•
1: Indicates that the transmit data is not recognized (NACK).
During broadcasting communication, however, the contents of the acknowledge bit are ignored.
(a) Last acknowledge bit of slave field
The last acknowledge bit of the slave field serves as NACK in any of the following cases, and
transmission is stopped.
•
If the parity of the master address bit or slave address bit is incorrect
•
If a timing error (error in bit format) occurs
•
If a slave unit does not exist
(b) Last acknowledge bit of control field
The last acknowledge bit of the control field serves as NACK in any of the following cases, and
transmission is stopped.
•
If the parity of the control bit is incorrect
•
If control bit 3 is ‘1’ (write operation) when the slave reception enable flag (ENSLVRX) is not set (1)
Note
•
If the control bit indicates reading of data (3H or 7H) when the slave transmission enable flag
(ENSLVTX) is not set (1)
Note
•
If a unit other than that has set locking requests 3H, 6H, 7H, AH, BH, EH, or FH of the control bit when
locking is set
•
If the control bit indicates reading of lock addresses (4H, 5H) even when locking is not set
•
If a timing error occurs
•
If the control bit is undefined
Note
Refer to
19.3.2 (1) IEBus control register (BCR)
.
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 broadcasting
communication, communication is maintained and the data request interrupt
(INTIE1) or IEBus end interrupt (INTIE2) is generated.
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