CHAPTER 19 IEBus CONTROLLER (V850/SB2)
User’s Manual U13850EJ4V0UM
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(c) Slave status return operation
When the IEBus receives a request to transfer from master to slave status or a lock address request
(control data: 0H, 6H), 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 acknowledgement of a slave status or lock request will cause the STATUSF
flag (bit 4 of the ISR register) to be set and the status interrupt (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 19-16. Interrupt Generation Timing (for (1), (3), and (4))
INTIE2
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)
Содержание MPD703030A
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