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CHAPTER 17
IEBus CONTROLLER (
PD178096A, 178098A, 178F098 ONLY)
User’s Manual U12790EJ2V0UD
(5) IEBus control data register (CDR)
(a) Master unit
The data of the lower 4 bits is reflected in the data transmitted in the control field. When a master request
is issued, this register must be set in advance before starting communication.
(b) Slave unit
The data received in the control field is written to the lower 4 bits.
When the status transmission flag (STATUSF) of the IEBus interrupt status register (ISR) is set, an interrupt
(INTIE2) is issued, and each processing should be performed by software, according to the value of the lower
4 bits of CDR.
Figure 17-15. Format of IEBus Control Data Register (CDR)
Cautions 1. Because the slave unit must judge whether the received data is a “command” or “data”,
it must read the value of this register after completing communication.
2. Instructions in Read Modify Write mode (such as XCH and ROL4) cannot be used for
CDR.
3. If the master unit sets an undefined value, NACK is returned from the slave unit, and
communication is aborted. During broadcast communication, however, the master
unit continues communication without recognizing ACK/NACK; therefore, make sure
not to set an undefined value to this register during broadcast communication.
4. In the case of defeat in a bus conflict and a slave status request is received from the
unit that won, the IEBus telegraph length register (DLR) is fixed to “01H”. Therefore,
when a re-request of the master follows, the appointed telegraph length must be set
to DLR.
0
Read slave status
Undefined
Read data and lock
Read lock address (lower 8 bits)
Read lock address (higher 4 bits)
Read slave status and unlock
Read data
Undefined
Write command and lock
Write data and lock
Undefined
Write command
Write data
CDR3
0
1
Function
CDR
0
CDR3
CDR2
CDR1
CDR0
CDR2
0
1
0
1
CDR1
0
1
0
1
0
1
0
1
CDR0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
After reset: 01H
R/W
Address: FFB8H