5-53
C2K User’s Guide
Resources
5.2.7 USART Divisor Latch Registers
The USART includes a programmable baud-rate generator to divide the reference clock down to
the serial data rate. The divisor is a 16-bit value contained in two byte-wide registers: one for the
MSB and one for the LSB. In asynchronous mode, the clock is set to 16 x the bit rate, while in the
synchronous mode, the clock is set to 1 x the bit rate.
USART Divisor (LSB) Register
Bit(s)
Field
Default
Description
7 - 0
0x00
USART Divisor (MSB) Register
Bit(s)
Field
Default
Description
7 - 0
0x00
Table 5-13 shows the divisor values for some common serial data rates with a 14.7692MHz
(48.0MHz x 4 /13) reference clock.
Address offset:
USART + Base +0x0
DLAB:
1
Access:
Read/write
DIV[7–0]
LSB of baud-rate generator divisor.
Address offset:
USART + Base + 0x2
DLAB:
1
Access:
Read/write
DIV[15–8]
MSB of baud-rate generator divisor.
Table 5-13
Baud-rate divisor settings
Baud
Rate
Sync
Mode
Divisor
Frequency
Error (%)
300
0
3076
+0.03
1200
0
770
+0.16
2400
0
384
+0.16
9600
0
96
+0.16
19200
0
48
+0.16
38400
0
24
+0.16
57600
0
16
+0.16
115.2k
0
8
+0.16
230.4k
0
4
+0.16
460.8k
0
2
+0.16
921.6k
1
16
+0.16
1.8432M
1
8
+0.16
3.6864M
1
4
+0.16
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com