Nxp Semiconductors UM10237 ユーザーズマニュアル
UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
440 of 792
NXP Semiconductors
UM10237
Chapter 16: LPC24XX Universal Asynchronous Receiver/Transmitter
4.12.1.1
Example 1: PCLK = 14.7456 MHz, BR = 9600
According to the the provided algorithm DL
est
= PCLK/(16 x BR) = 14.7456 MHz / (16 x
9600) = 96. Since this DL
est
is an integer number, DIVADDVAL = 0, MULVAL = 1,
DLM = 0, and DLL = 96.
4.12.1.2
Example 2: PCLK = 12 MHz, BR = 115200
According to the the provided algorithm DL
est
= PCLK/(16 x BR) = 12 MHz / (16 x 115200)
= 6.51. This DL
est
is not an integer number and the next step is to estimate the FR
parameter. Using an initial estimate of FR
est
= 1.5 a new DL
est
= 4 is calculated and FR
est
is recalculated as FR
est
= 1.628. Since FRest = 1.628 is within the specified range of 1.1
and 1.9, DIVADDVAL and MULVAL values can be obtained from the attached look-up
table.
table.
The closest value for FRest = 1.628 in the look-up
is FR = 1.625. It is
equivalent to DIVADDVAL = 5 and MULVAL = 8.
Based on these findings, the suggested UART setup would be: DLM = 0, DLL = 4,
DIVADDVAL = 5, and MULVAL = 8. According to
DIVADDVAL = 5, and MULVAL = 8. According to
UART’s is 115384. This
rate has a relative error of 0.16% from the originally specified 115200.
4.13 UARTn Transmit Enable Register (U0TER - 0xE000 C030, U2TER -
0xE007 8030, U3TER - 0xE007 C030)
LPC2400’s UnTER enables implementation of software flow control. When TXEn=1,
UARTn transmitter will keep sending data as long as they are available. As soon as TXEn
becomes 0, UARTn transmission will stop.
UARTn transmitter will keep sending data as long as they are available. As soon as TXEn
becomes 0, UARTn transmission will stop.
Table 393. Fractional Divider setting look-up table
FR
DivAddVal/
MulVal
MulVal
FR
DivAddVal/
MulVal
MulVal
FR
DivAddVal/
MulVal
MulVal
FR
DivAddVal/
MulVal
MulVal
1.000
0/1
1.250
1/4
1.500
1/2
1.750
3/4
1.067
1/15
1.267
4/15
1.533
8/15
1.769
10/13
1.071
1/14
1.273
3/11
1.538
7/13
1.778
7/9
1.077
1/13
1.286
2/7
1.545
6/11
1.786
11/14
1.083
1/12
1.300
3/10
1.556
5/9
1.800
4/5
1.091
1/11
1.308
4/13
1.571
4/7
1.818
9/11
1.100
1/10
1.333
1/3
1.583
7/12
1.833
5/6
1.111
1/9
1.357
5/14
1.600
3/5
1.846
11/13
1.125
1/8
1.364
4/11
1.615
8/13
1.857
6/7
1.133
2/15
1.375
3/8
1.625
5/8
1.867
13/15
1.143
1/7
1.385
5/13
1.636
7/11
1.875
7/8
1.154
2/13
1.400
2/5
1.643
9/14
1.889
8/9
1.167
1/6
1.417
5/12
1.667
2/3
1.900
9/10
1.182
2/11
1.429
3/7
1.692
9/13
1.909
10/11
1.200
1/5
1.444
4/9
1.700
7/10
1.917
11/12
1.214
3/14
1.455
5/11
1.714
5/7
1.923
12/13
1.222
2/9
1.462
6/13
1.727
8/11
1.929
13/14
1.231
3/13
1.467
7/15
1.733
11/15
1.933
14/15