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CHAPTER 18 IEBus CONTROLLER (V850/SC2)
512
User’s Manual U15109EJ3V0UD
(5) Control field
The master outputs the operation it requires the slave to perform, by using this field.
The configuration of the control field is as shown in Figure 18-4.
If the parity following the control bit is even and if the slave unit can execute the function required by the
master unit, the slave unit outputs an acknowledge signal and starts outputting the telegraph length field. If the
slave unit cannot execute the function required by the master unit even if the parity is even, or if the parity is
odd, the slave unit does not output the acknowledge signal, and returns to the standby (monitor) status.
The master unit starts outputting the telegraph length field after confirming the acknowledge signal.
If the master cannot confirm the acknowledge signal, the master unit enters the standby status, and
communication ends. During broadcast communication, however, the master unit does not confirm the
acknowledge signal, and starts outputting the telegraph length field.
Table 18-2 shows the contents of the control bits.
Table 18-2. Contents of Control Bits
Bit 3
Note 1
Bit 2
Bit 1
Bit 0
Function
0
0
0
0
Reads slave status
0
0
0
1
Undefined
0
0
1
0
Undefined
0
0
1
1
Reads data and locks
Note 2
0
1
0
0
Reads lock address (lower 8 bits)
Note 3
0
1
0
1
Reads lock address (higher 4 bits)
Note 3
0
1
1
0
Reads slave status and unlocks
Note 2
0
1
1
1
Reads data
1
0
0
0
Undefined
1
0
0
1
Undefined
1
0
1
0
Writes command and locks
Note 2
1
0
1
1
Writes data and locks
Note 2
1
1
0
0
Undefined
1
1
0
1
Undefined
1
1
1
0
Writes command
1
1
1
1
Writes data
Notes 1.
The telegraph length bit of the telegraph length field and data transfer direction of the data field
change as follows depending on the value of bit 3 (MSB).
If bit 3 is ‘1’: Transfer from master unit to slave unit
If bit 3 is ‘0’: Transfer from slave unit to master unit
2.
This is a control bit that specifies locking or unlocking (refer to
18.1.7 (4) Locking and unlocking
).
3.
The lock address is transferred in 1-byte (8-bit) units and is configured as follows:
MSB
Lower 8 bits
Undefined
Higher 4 bits
Control bit: 4H
Control bit: 5H
LSB