AN2502 Freescale Semiconductor / Motorola, AN2502 Datasheet - Page 19

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

Half-Duplex Maximum
Baud Rate
MOTOROLA
Data
Data
Bits
Bits
NOTE:
8
8
9
8
9
8
9
8
9
8
9
8
9
Table 11
required for the MCU to implement a specific application.
Parity
Parity
None
None
None
None
None
Even
Even
Even
Even
Odd
Odd
Odd
Odd
Using Two Channels of the HC08 TIM to Achieve a Full-Duplex Software SCI
does not consider latency for other interrupts, so the user must compute the final performance
Table 11. Maximum Baud Rates for Enhanced and Normal Modes
SCI Implementation
Enhanced Mode
Stop
Stop
Bits
Bits
Normal Mode
1
1
1
1
1
1
1
2
2
2
2
2
2
When receiving data in half-duplex operation, the reception line must be
checked within 30% and 70% of 1 bit-time. When adding 1.3 of 1 bit-time for
the reception of the first bit as shown in
to be added to the reception channel register is 1 bit-time multiplied by 1.3
minus pin check latency. The resulting number of counts to be added must be
greater than 1 bit-time for the half-duplex operation. This result gives the first
boundary condition for half-duplex operation.
When receiving or transmitting data in half-duplex, the interrupt service
routines must be performed in fewer CPU cycles than the bit-time calculated for
the desired baud rate, which is another boundary condition. The resulting
formula for the maximum baud rate in half-duplex is:
Maximum baud rate = f
Freescale Semiconductor, Inc.
Cycles
Cycles
Max
Max
168
163
167
162
167
162
151
146
151
146
151
146
For More Information On This Product,
Rx
Rx
73
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Cycles
Cycles
Max
Max
137
142
137
142
137
142
151
156
151
156
151
156
Tx
88
Tx
Bus
/(MAX(Latency/0.3, Max Cycles Rx, Max Cycles Tx)
27927.27
14628.57
15077.30
14716.17
15170.37
14716.17
15170.37
16275.50
15753.85
16275.50
15753.85
16275.50
15753.85
2.4576
2.4576
MHz
MHz
f
f
Bus
Bus
Half-Duplex
Half-Duplex
90909.09
47619.05
49079.75
47904.19
49382.72
47904.19
49382.72
52980.13
51282.05
52980.13
51282.05
52980.13
51282.05
Figure
Maximum Baud Rates
MHz
MHz
f
f
Bus
Bus
8
8
15, the number of timer counts
11170.91
7175.47
6922.82
7175.47
6922.82
7175.47
6922.82
6510.20
6301.54
6510.20
6301.54
6510.20
6301.54
2.4576
2.4576
MHz
MHz
f
f
Bus
Bus
Full-Duplex
Full-Duplex
36363.64
23357.66
22535.21
23357.66
22535.21
23357.66
22535.21
20512.82
20512.82
20512.82
21192.05
21192.05
21192.05
MHz
MHz
f
f
Bus
Bus
8
8
AN2502/D
Modes
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