cop87l88gw National Semiconductor Corporation, cop87l88gw Datasheet - Page 27

• Manufacturer Part Number: cop87l88gw
• Description: One-time Programmable Otp Microcontroller
• Manufacturer: National Semiconductor Corporation

Baud Clock Generation
As shown in Table V a Prescaler Factor of 0 corresponds to
NO CLOCK This condition is the UART power down mode
where the UART clock is turned off for power saving pur-
pose The user must also turn the UART clock off when a
different baud rate is chosen
The correspondences between the 5-bit Prescaler Select
and Prescaler factors are shown in Table V There are many
ways to calculate the two divisor factors but one particularly
effective method would be to achieve a 1 8432 MHz fre-
quency coming out of the first stage The 1 8432 MHz pre-
scaler output is then used to drive the software programma-
ble baud rate counter to create a 16x clock for the following
baud rates 110 134 5 150 300 600 1200 1800 2400
3600 4800 7200 9600 19200 and 38400 (Table IV) Other
baud rates may be created by using appropriate divisors
The 16x clock is then divided by 16 to provide the rate for
the serial shift registers of the transmitter and receivers
Note The entries in Table IV assume a prescaIer output of 1 8432 MHz In
asynchronous mode the baud rate could be as high as 625k
134 5 (134 58)
110 (110 03)
(1 8432 MHz PrescaIer Output)
TABLE IV Baud Rate Divisors
19200
38400
Baud
Rate
1200
1800
2400
3600
4800
7200
9600
150
300
600
Divisor
Baud Rate
1046
855
767
383
191
95
63
47
31
23
15
11
b
5
2
(Continued)
1 (N-1)
27
Prescaler
TABLE V Prescaler Factors
Select
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
NO CLOCK
Prescaler
Factor
10 5
11 5
12 5
13 5
14 5
15 5
1 5
2 5
3 5
4 5
5 5
6 5
7 5
8 5
9 5
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
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