7702 Datasheet, PDF (200/522 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER

SERIAL I/O
7.4 Clock asynchronous serial I/O (UART) mode
7.4.1 Transfer rate (frequency of transfer clock)
The transfer rate is determined by the BRGi (addresses 3116, 3916).
When setting “n” into BRGi (n = “0016” to “FF16”), BRGi divides the count source frequency by n + 1. The
divided clock by BRGi is further divided by 16 and the resultant clock becomes the transfer clock. Accordingly,
the value “n” is expressed by the following formula.
F
n = _{16 ! B} — 1
n: Value set into BRGi
F: BRGi’s count source frequency
B: Transfer rate
An internal clock or an external clock can be selected as the BRGi’s count source with the internal/external
clock select bit (bit 3 at addresses 3016, 3816). When an internal clock is selected, the clock selected with
the BRG count source select bits (bits 0 and 1 at addresses 3416, 3C16) becomes the BRGi’s count source.
When an external clock is selected, the clock input to the CLKi pin becomes the BRGi’s count source.
Tables 7.4.3 and 7.4.4 are list the setting examples of transfer rate. Set the same transfer rate between
the transmitter and the receiver.
Table 7.4.3 Setting examples of transfer rate (1)
Transfer
f(XIN) = 8 MHz
rate (bps) BRGi count BRGi setting Actual time
source
value : n
(bps)
75
f 512
12 (0C16)
75.12
110
f 64
70 (4616)
110.04
134.5
f 64
57 (3916)
134.70
150
f 64
51 (3316)
150.24
300
f 64
25 (1916)
300.48
600
f 64
12 (0C16)
600.96
1200
f 16
25 (1916)
1201.92
2400
f 16
12 (0C16)
2403.85
4800
f2
51 (3316)
4807.69
9600
f2
25 (1916)
9615.39
19200
f2
12 (0C16)
19230.77
31250
f2
7 (0716)
31250.00
62500
f2
3 (0316)
62500.00
125000
f2
1 (0116)
125000.00
250000
f2
0 (0016)
250000.00
500000
f2
BRGi count
source
f512
f64
f64
f64
f64
f64
f16
f16
f2
f2
f2
f2
f2
f2
f2
f2
f(XIN) = 16 MHz
BRGi setting Actual time
value : n
(bps)
25 (1916)
75.12
141 (8D16)
110.04
115 (7316)
134.70
103 (6716)
150.24
51 (3316)
300.48
25 (1916)
600.96
51 (3316)
1201.92
25 (1916)
2403.85
103 (6716)
4807.69
51 (3316)
9615.39
25 (1916)
19230.77
15 (0F16)
31250.00
7 (0716)
62500.00
3 (0316)
125000.00
1 (0116)
250000.00
0 (0016)
500000.00
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7702/7703 Group User’s Manual