Panasonic MN103001G/F01K User Manual download pdf (Page 348)

Serial Interface

13-46

Division ratio 1 = INT (IOCLK frequency / bit rate/127) + 1

Division ratio 2 = INT (IOCLK frequency / bit rate/division ratio 1 + 0.5)

Subtract 1 from the value for division ratio 2 that was derived through the above equations, and write the result in

SC3TIM.

If the value of division ratio 1 is 2 or higher, timer 2 or timer 8 must be used to divide the clock. Set SC3CK1 and

0 in the serial 3 control register SC3CTR to "01", and then set the control registers of timer 2 so that the clock is

divided by the value of division ratio 1. (Otherwise, set SC3CK1 and 0 in the serial 3 control register SC3CTR to

"11", and then set the control registers of timer 8 so that the clock is divided by the value of division ratio 1.)

If the value of division ratio 1 is 1, set SC3CK1 and 0 in the serial 3 control register SC3CTR to "00" and select

IOCLK.

The error versus the actual bit rate is calculated as follows:

Bit rate error = ABS (division ratio 1 x division ratio 2 x bit rate / IOCLK frequency – 1)

For example, when a 15 MHz IOCLK signal is used and transfer is conducted at a rate of 38.4 kbit/s, the timer

function is used to divide the clock signal. According to the equations shown above, division ratio 1 is 4 and

division ratio 2 is 98.

Set TM2BR = 3 in the timer 2 base register and SC3TIM = 97 in the serial 3 timer register, and set SC3CK1 and 0

to "01".

According to the equation shown above, the bit rate error is 0.35 %.

Tables 13-4-2 through 13-4-4 show typical examples.

Table 13-4-2 Bit Rates (1) (When IOCLK = 15 MHz)

Bit rate (bit/s) Division ratio 1 Division ratio 2 Bit rate error

230 400 1 65 0.16 %

115 200 2 65 0.16 %

56 000 3 89 0.32 %

38 400 4 98 0.35 %

19 200 7 112 0.35 %

9 600 13 120 0.16 %

4 800 25 125 0.00 %

2 400 50 125 0.00 %

1 200 99 126 0.21 %

600 197 127 0.08 %

300 394 127 0.08 %

150 788 127 0.08 %

Note: When using a timer to divide the clock signal, subtract 1 from the value of division ratio 1 as derived from

the equations on the top of this page, and write the result in the timer base register. For details, refer to the

chapter on the 8-bit timers.

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Panasonic MN103001G/F01K User Manual Page 348