m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 293

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

SERIAL I/O
11.4 Clock asynchronous serial I/O (UART) mode
Table 11.4.3 Setting examples of transfer rate (1)
Note: This applies when the peripheral device’s clock select bits 1, 0 (bits 7, 6 at address BC
11-38
Table 11.4.4 Setting examples of transfer rate (2)
Note: This applies when the peripheral device’s clock select bits 1, 0 (bits 7, 6 at address BC
11.4.1 Transfer rate (Frequency of transfer clock)
The transfer rate is determined by the BRGi (addresses 31
When “n” is set into BRGi, BRGi divides the count source frequency by (n + 1). The BRGi’s output is further divided
by 16, and the resultant clock becomes the transfer clock. Accordingly, “n” is expressed by the following formula.
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 30
with the BRG count source select bits (bits 0 and 1 at addresses 34
count source. When an external clock is selected, the clock input to the CLK
source.
Be sure to set the same transfer rate for both transmitter and receiver sides. Tables 11.4.3 and 11.4.4 list
the setting examples of transfer rate.
Each of the values, listed in these tables, realizes the actual transfer rate of which error toward an ideal
transfer rate is within 1 %.
rate (bps)
rate (bps)
Transfer
Transfer
14400
19200
31250
38400
14400
19200
31250
38400
1200
2400
4800
9600
1200
2400
4800
9600
n =
300
600
300
600
16
F
count source
count source
B
BRGi’s
BRGi’s
— 1
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
64
16
16
16
2
2
2
2
2
64
16
16
2
2
2
2
2
2
2
f
f
sys
sys
value: n (Note)
value: n (Note)
207 (CF
127 (7F
127 (7F
103 (67
103 (67
= 19.6608 MHz
= 15.9744 MHz
BRGi’s set
BRGi’s set
42 (2A
12 (0C
63 (3F
63 (3F
31 (1F
63 (3F
31 (1F
15 (0F
51 (33
51 (33
51 (33
34 (22
25 (19
15 (0F
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
7905 Group User’s Manual Rev.1.0
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16
n: Value set in BRGi (00
F: BRGi’s count source frequency (Hz)
B: Transfer rate (bps)
, B0
Actual time
Actual time
31200.00
14288.37
19200.00
38400.00
14262.86
19200.00
38400.00
1200.00
2400.00
4800.00
9600.00
1200.00
2400.00
4800.00
9600.00
(bps)
(bps)
16
300.00
600.00
300.00
600.00
). When an internal clock is selected, the clock selected
count source
count source
16
, 39
BRGi’s
BRGi’s
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
f
16
64
16
16
2
2
2
2
64
16
16
2
2
2
2
2
2
, B1
16
16
16
to FF
, 3C
).
value: n (Note)
value: n (Note)
207 (CF
129 (81
129 (81
103 (67
103 (67
i
BRGi’s set
BRGi’s set
f
f
12 (0C
42 (2A
15 (0F
64 (40
64 (40
64 (40
19 (13
51 (33
51 (33
51 (33
25 (19
pin becomes the BRGi’s count
16
sys
sys
16
, B4
)
= 20 MHz
= 16 MHz
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
) becomes the BRGi’s
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Actual time
Actual time
14534.88
31250.00
38461.51
19230.77
31250.00
1201.92
2403.85
4807.69
9615.38
1201.92
4807.69
9615.38
300.48
600.96
(bps)
300.48
600.96
16
(bps)
16
) = “00
) = “00
2
2
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