UM10147_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 28 April 2008
58 of 134
NXP Semiconductors
UM10147
P89LPC952/954 User manual
10.7 Updating the BRGR1 and BRGR0 SFRs
The baud rate SFRs, BRGR1_n and BRGR0_n must only be loaded when the Baud Rate
Generator is disabled (the BRGEN_0 bit in the BRGCON_n register is logic 0). This
avoids the loading of an interim value to the baud rate generator.
(CAUTION: If either
BRGR0_n or BRGR1_n is written when BRGEN_n = 1, the result is unpredictable.)
Table 45.
UART baud rate generation
SnCON.7
(SM0)
SnCON.6
(SM1)
PCON.7
(SMOD1)
BRGCON_n
.1 (SBRGS)
Receive/transmit baud rate for UART
0
0
X
X
CCLK
⁄
16
0
1
0
0
CCLK
⁄
(256
−
TH1)64
1
0
CCLK
⁄
(256
−
TH1)32
X
1
CCLK
⁄
((BRGR1_n, B16)
1
0
0
X
CCLK
⁄
32
1
X
CCLK
⁄
16
1
1
0
0
CCLK
⁄
(256
−
TH1)64
1
0
CCLK
⁄
(256
−
TH1)32
X
1
CCLK
⁄
((BRGR1_n, B16)
Table 46.
Baud Rate Generator Control register (BRGCON_0 - address BDh) bit allocation
Bit
7
6
5
4
3
2
1
0
Symbol
--
-
-
-
-
-
SBRGS_0 BRGEN_0
Reset
x
x
x
x
x
x
0
0
Table 47.
Baud Rate Generator Control register (BRGCON - address BDh) bit description
Bit Symbol
Description
0
BRGEN
_0
Baud Rate Generator 0 Enable. Enables the baud rate generator. BRGR1_0 and
BRGR0_0 can only be written when BRGEN_0 = 0.
1
SBRGS
_0
Select Baud Rate Generator 0 as the source for baud rates to UART0 in modes 1
and 3 (see
for details)
2:7 -
reserved
Table 48.
Baud Rate Generator Control register (BRGCON_1 - address FFB3h) bit
allocation
Bit
7
6
5
4
3
2
1
0
Symbol
--
-
-
-
-
-
SBRGS_1 BRGEN_1
Reset
x
x
x
x
x
x
0
0
Table 49.
Baud Rate Generator Control register (BRGCON_1 - address FFB3h) bit
description
Bit Symbol
Description
0
BRGEN
_1
Baud Rate Generator 1Enable. Enables the baud rate generator. BRGR1_1 and
BRGR0_1 can only be written when BRGEN_1 = 0.
1
SBRGS
_1
Select Baud Rate Generator 1as the source for baud rates to UART1 in modes 1
and 3 (see
for details)
2:7 -
reserved