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8XC196MC, MD, MH USER’S MANUAL
5-50
Figure 5-24. Synchronous SIO Receive Mode — End-of-PTS Interrupt Routine Flowchart
5.6.6.3 Asynchronous SIO Transmit Mode Example
In asynchronous serial I/O (ASIO) transmit mode, an EPA channel controls the transmission baud
rate by generating an interrupt whenever a match occurs between the EPA event-time register and
a timer register. The PTS shifts a data bit out onto a port pin that is configured to function as the
Transmit Data signal (TXD) when the selected EPA channel generates a compare interrupt (Fig-
ure 5-25). In ASIO transmit mode, the PTS automatically transmits up to 16 bits (data + 1 optional
parity + 1 stop bit). The maximum number of data bits is 14 with parity, or 15 without.
A3275-01
End-Of-PTS Interrupt
Save Critical Data
Set-up next data reception
- Clear DATA register
- Reload PTSCOUNT and PTSCON1 registers
- Select PTS service for EPA channel
- Re-initialize the EPA channel
Load Critical Data
Return
R_COUNT = R_COUNT - 1
Y
N
R_COUNT = 0?
Save Received Data
Disable EPA Channel
Clear Interrupt Request Bit
RXDDONE = 1