AN2502 Freescale Semiconductor / Motorola, AN2502 Datasheet - Page 11

• Manufacturer Part Number: AN2502
• Description: Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
The transmission of data bits is performed by the channel interrupt service
routine, which generates output compares depending on the data bit value to
be sent.
In the interrupt service routine of the transmission channel, the channel
registers are read and 1 bit-time is added to generate the next output compare
for the next data bit transmission.
As shown in
transmission shift register, and the output compare level is configured
depending on the value of each bit to be transmitted. The process is repeated
until the last data bit is transmitted.
In the last bit transmission interrupt, the channel is configured as set on output
compare to send the stop bit. This is shown in
figure, the
transmission is pending, the channel is configured as clear on output compare
to send the next start bit after 1 bit-time.
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flag is checked before turning off the channel, so if a
Figure 20. First Data Bit Transmission
21, each bit to be transmitted is shifted out of the
Figure 21. Data Bits Transmission
1 BIT-TIME
DATA BIT
FIRST
START BIT
1 BIT-TIME
OUTPUT COMPARE
LEVEL DEPENDING ON
DATA BIT TRANSMITTED
DATA BIT
SECOND
DATA BIT
FIRST
Figure
22. As shown in this
AN2502/D
Modes
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