CHAPTER 19 IEBus CONTROLLER (V850/SB2)
User’s Manual U13850EJ4V0UM
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(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 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 broadcasting 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 error
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 error only occurs in individual communication. ACK and
NACK are not discriminated in broadcasting communication.
Remark:
An interrupt is generated if NACK is received in a field other than the data
field.
•
Underrun
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
Occurrence conditions: The data interrupt request (INTIE1) that stores each byte of data in the IEBus
data register (DR), and the DR register is read by DMA or 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 acknowledgement is not returned
in the ACK period of this data, resulting in the retransmission of the data by
the transmit unit. Consequently, the IEBus transfer counter (CCR) is
decremented, whereas the IEBus communication success counter (SCR) is
not. In broadcasting communication reception, reception is stopped by the
occurrence of a communication error (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.