AN2502 Freescale Semiconductor / Motorola, AN2502 Datasheet - Page 18

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

AN2502/D
Example Typical
Baud Rates
18
Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
This code shows that the pin check latency is: 3 + 9 + 2 + 4 + 5 + 1 + 2 = 26 +
(0/+5) CPU bus cycles. In the code listings at the end of the document, the user
can also find the duration of the instructions preformed prior to the pin check
instruction for the enhanced mode.
Using an external crystal oscillator of 9.8304 MHz on the MC68HC908JK3, no
prescaler selection for the TIM, and a pin check latency of 26 timer cycles for
the normal operation of the SCI, the values of typical baud rates would be as
shown in
Using the same crystal frequency and considering that the pin check latency in
the enhanced mode is 28 timer cycles with no prescaler, the values of the baud
rates are shown in
The maximum baud rate is dependent on the TIM frequency and the maximum
number of cycles that each of the interrupts uses. A summary of the maximum
baud rates depending on SCI configuration is depicted in
maximum baud rates are calculated from the maximum number of cycles that
each interrupt takes during transmission and reception.
Freescale Semiconductor, Inc.
For More Information On This Product,
BIT1HI:BIT1LO
BIT1HI:BIT1LO
BITHI:BITLO
BITHI:BITLO
Table
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9.
Table 10. Baud Rates for Enhanced Mode
Table 9. Baud Rates for Normal Mode
Table
10.
0x012E
0x0100
0x0133
0x0100
9600
9600
0x027B
0x0200
0x0280
0x0200
4800
4800
Baud Rate
Baud Rate
0x0400
0x0519
0x0400
0x0514
2400
2400
Table
0x0A4C
0x0800
0x0800
0x0A47
11. These
1200
1200
MOTOROLA