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CHAPTER 17
IEBus CONTROLLER (
PD178096A, 178098A, 178F098 ONLY)
User’s Manual U12790EJ2V0UD
(f)
Communication error triggers
Timing error
Occurrence conditions: Occurs if the high/low level width of the communication bit has shifted from the
prescribed value.
Remark:
The respective prescribed values are set in the bit processing block and monitored
by the internal 8-bit timer. An interrupt is generated when a timing error occurs.
Parity error
Occurrence conditions: Occurs if the generated parity and the received parity in each field do not match
when the IEBus is a receiving unit.
Remark:
During individual communication, an interrupt is generated if a parity error occurs
in a field other than the data field.
During broadcast communication, an interrupt is generated even if a parity error
occurs in the data field.
Restriction:
If there is a slave request that has lost in arbitration to a broadcast request, no
interrupt is generated, even if a parity error occurs.
NACK reception
Occurrence conditions: This error occurs when NACK is received during the ACK period in each of the
slave address, control, and telegraph length fields during individual communication,
regardless of whether the unit is the master or a slave unit.
A NACK reception only occurs in individual communication. ACK and NACK are
not discriminated in broadcast communication.
Remark:
An interrupt is generated if NACK is received in a field other than the data field.
Underrun error
Occurrence conditions: Occurs during data transmission if there was insufficient time to write the next
transmit data to the IEBus data register (DR) before ACK reception.
Remark:
An interrupt is generated if an underrun occurs.
Overrun error
Occurrence conditions: The data interrupt request (INTIE1) that stores each byte of data in the IEBus data
register (DR) is generated, and the DR register is read by software. An overrun
error occurs if this reading processing is late and its timing becomes that of the
next data reception.
Remark:
In individual communication reception, an acknowledgment is not returned in the
ACK period of this data, resulting in the retransmission of the data by the
transmitting unit. Consequently, the IEBus transfer counter (CCR) is decremented,
whereas the IEBus communication success counter (SCR) is not. In broadcast
communication reception, reception is stopped by the occurrence of a communication
error interrupt request (INTIE2), at which time the DR register is not updated. The
STATRX flag (bit 1 of the SSR register) also remains set (1) without generating
INTIE1. The overrun state is released at the timing of the next data reception
following the reading of DR.