Datasheet

Table Of Contents
Section 13 Serial Communication Interface
REJ09B0140-0900 Rev. 9.00 Page 407 of 846
Sep 16, 2010
H8S/2215 Group
Example for 921.6 kbps when φ = 16 MHz
Generation of clock with 923.077 kbps average transfer rate by means of TPU (ACS2 to 0 = B'100)
(1) An 8 MHz base clock provided by TPU_1 is multiplied by 12/13 by TPU_2 to generate a 7.3846 MHz base clock
(2) By making 1 bit = 8 base clocks, the average transfer rate is made 7.3846 MHz/8 = 923.077 kbps.
Sample TPU and SCI settings
TMDR_1 = TMDR_2 = H'C2 [PWM mode 1]
TCR_1 = H'20 [TCNT_1 incremented on rising edge of ø/1, TCNT_1 cleared by TGRA_1 compare match]
TGRB_1 = H'0000, TGRA_1 = H'0001
TIOR_1 = H'21 [1 output on TGRB_1 compare match, TIOCA1 initial output 0, 0 output on TGRA_1 compare match]
TCR_2 = H'2C [TCNT_2 incremented on falling edge of TCLKA (TIOCA1), TCNT_2 cleared by TGRA_2 compare match]
TGRB_2 = H'0000, TGRA_2 = H'000C
TIOR_2 = H'21 [1 output on TGRB_2 compare match, TIOCA2 initial output 0, 0 output on TGRA_2 compare match]
SEMR = H'0C (ABCS = 1, ACS2-0 = B'100)
Main clock: 16 MHz
TIOCA1(TPU_1) output = 8 MHz
TIOCA2 (TPU_2) output
Internal base clock
= 8 MHz x 12/13
= 7.3846 MHz
1 bit = 8 base clocks*
Average transfer rate = 7.3846 MHz/8 = 923.077 kbps
Average error relative to 921.6 kbps = +0.16%
Note: * As the base clock synchronization varies, so does the length of one bit.
1 1
1
2345678910111213 12345678910111213
12345678
12345678
9101112 1
1
234
5
1234 678
56789101112
12345678
8 MHz
7.3846 MHz
Figure 13.5 Example of Average Transfer Rate Setting when TPU Clock Is Input (1)