
392
CHAPTER 17
IEBus CONTROLLER (
PD178096A, 178098A, 178F098 ONLY)
User’s Manual U12790EJ2V0UD
(c) Slave status return operation
When the IEBus receives a request to transfer from master to slave status (control data: 0H, 6H) or a lock
address request (4H, 5H), whether ACK in the control field is returned or not depends on the status of the
IEBus unit.
(1) If 0H or 6H control data was received in the unlocked state
→ ACK returned
(2) If 4H or 5H control data was received in the unlocked state
→ ACK not returned
(3) If 0H, 4H, 5H or 6H control data was received in the locked
state from the unit that sent the lock request
→ ACK returned
(4) If 0H, 4H, or 5H control data was received in the locked state
from other than the unit that sent the lock request
→ ACK returned
(5) If 6H control data was received in the locked state from other
than the unit that sent the lock request
→ ACK not returned
In all of the above cases, the acknowledgment of a slave status or lock address request will cause the
STATUSF flag (bit 4 of the ISR register) to be set and the status interrupt request (INTIE2) to be generated.
The generation timing is at the end of the control field parity bit (at the start of the ACK bit). However, if ACK
is not returned, a NACK error is generated after the ACK bit, and communication is terminated.
Figure 17-16. Interrupt Generation Timing (for (1), (3), and (4))
Figure 17-17. Interrupt Generation Timing (for (2) and (5))
INTIE2
L
Flag set by reception
of 0H, 4H, 5H, 6H
IEBus sequence
Flag reset by CPU processing
Control field
Telegraph length field
STATUSF flag
Internal NACK flag
Control bits (4 bits)
Parity bit (1 bit)
ACK bit (1 bit)
Telegraph length bits (8 bits)
INTIE2
Flag set by reception
of 0H, 4H, 5H, 6H
IEBus sequence
Flag reset by
CPU processing
Error generated by
detection of NACK
Control field
STATUSF flag
Internal NACK flag
Control bits (4 bits)
Parity bit (1 bit)
ACK bit (1 bit)
Terminated by communication error