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(2) Lock address
When the lock address is read (control bit: 4H or 5H), the address (12 bits) of the master unit that has issued
the lock instruction is configured in 1-byte units as shown below and read.
(3) Data
If the control bit indicates reading of data (3H or 7H), the data in the data buffer of the slave unit is read by
the master unit.
If the control bit indicates writing of data (BH or FH), the data received by the slave unit is processed
according to the operation rule of that slave unit.
(4) Locking and unlocking
The lock function is used when a message is transferred in two or more communication frames.
The unit that is locked does not receive data from units other than the one that has locked the unit (does not
receive broadcasting communication).
A unit is locked or unlocked as follows:
(a) Locking
If the communication frame is completed without succeeding to transmit or receive data of the number of
bytes specified by the telegraph length bit after the telegraph length field has been transmitted or
received (ACK = 0) by the control bit that specifies locking (3H, AH, or BH), the slave unit is locked by the
master unit. At this time, the bit (bit 2) in the byte indicating the slave status is set to '1'.
(b) Unlocking
After transmitting or receiving data of the number of data bytes specified by the telegraph length bit in
one communication frame by the control bit that has specified locking (3H, AH, or BH), or the control bit
that has specified unlocking (6H), the slave unit is unlocked by the master unit. At this time, the bit
related to locking (bit 2) in the byte indicating the slave status is reset to '0'.
Locking or unlocking is not performed during broadcasting communication.
Locking and unlocking conditions are shown below.
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CHAPTER 19
IEBus CONTROLLER (V850/SB2)
Figure 19-8. Configuration of Lock Address
MSB
Control bit: 4H
Control bit: 5H
Undefined
User's Manual U13850EJ6V0UD
LSB
Lower 8 bits
Higher 4 bits
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