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17.1.6
Hardware Error Detection Capabilities
To improve the reliability of serial data exchange, the serial channel ASC provides an
error interrupt request flag that indicates the presence of an error and three (selectable)
error status flags in register CON that indicate which error has been detected during
reception. Upon completion of a reception, the error interrupt request line EIR will be
activated simultaneously with the receive interrupt request line RIR, if one or more of the
following conditions are met:
•
If the framing error detection enable bit CON.FEN is set and any of the expected stop
bits is not high, the framing error flag CON.FE is set, indicating that the error interrupt
request is due to a framing error (asynchronous operating modes only).
•
If the parity error detection enable bit CON.PEN is set in the modes where a parity bit
is received and the parity check on the received data bits proves false, the parity error
flag CON.PE is set, indicating that the error interrupt request is due to a parity error
(asynchronous operating modes only).
•
If the overrun error detection enable bit CON.OEN is set and the last character
received was not read out of the receive buffer by software or DMA transfer at the
time the reception of a new frame is complete, the overrun error flag CON.OE is set
indicating that the error interrupt request is due to an overrun error (Asynchronous
and Synchronous Modes).
17.1.7
Interrupts
Four interrupt sources are provided for serial channel ASC. Line TIR indicates a transmit
interrupt, TBIR indicates a transmit buffer interrupt, RIR indicates a receive interrupt, and
EIR indicates an error interrupt of the serial channel. The interrupt output lines TBIR,
TIR, RIR, and EIR are activated (active state) for two periods of the module clock
The cause of an error interrupt request EIR (framing, parity, overrun error) can be
identified by the error status flags CON.FE, CON.PE, and CON.OE.
Note: By contrast to the error interrupt request line EIR, the error status flags
CON.FE/CON.PE/CON.OE are not reset automatically but must be cleared by
software.
For normal operation (that is, other than error interrupt), the ASC provides three interrupt
requests to control data exchange via this serial channel:
•
TBIR is activated when data is moved from TBUF to the transmit shift register.
•
TIR is activated before the last bit of an asynchronous frame is transmitted, or after
the last bit of a synchronous frame has been transmitted.
•
RIR is activated when the received frame is moved to RBUF.
While the task of the receive interrupt handler is quite clear, the transmitter is serviced
by two interrupt handlers. This provides advantages for the servicing software.
User's Manual
ASC, V1.3 2007-11
Asynchronous/Synchronous Serial Interface (ASC)
17-19
TC1728
f
.
ASC
V1.0, 2011-12
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