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CHAPTER 18 IEBus CONTROLLER (V850/SC2)
User’s Manual U15109EJ3V0UD
517
Caution
Do not operate a master reception in broadcast communication, because the slave unit
cannot be defined and a data transfer cannot be performed correctly.
(8) Parity bit
The parity bit is used to check to see if the transmit data has no error.
The parity bit is appended to each data of the master address, slave address, control, telegraph length, and
data bits.
The parity is an even parity. If the number of bits in data that are ‘1’ is odd, the parity bit is ‘1’. If the number of
bits in the data that are ‘1’ is even, the parity bit is ‘0’.
(9) Acknowledge bit
During normal communication (communication from one unit to another), an acknowledge bit is appended to
the following locations to check to see 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 broadcast communication, however, the content of the acknowledge bit is 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)
(refer to
18.3.2 (1) IEBus Control Register (BCR)
)
•
If the control bit indicates reading of data (3H or 7H) when the slave transmission enable flag
(ENSLVTX) is not set (1) (refer to
18.3.2 (1) IEBus Control Register (BCR)
)
•
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