© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
User manual
Rev. 01 — 15 August 2005
116
Philips Semiconductors
UM10139
Volume 1
Chapter 10: UART1
10.3.4 UART1 Fractional Divider Register (U1FDR - 0xE001 0028)
The UART1 Fractional Divider Register (U1FDR) controls the clock pre-scaler for the baud
rate generation and can be read and written at user’s discretion. This pre-scaler takes the
VPB clock and generates an output clock per specified fractional requirements.
This register controls the clock pre-scaler for the baud rate generation. The reset value of
the register keeps the fractional capabilities of UART1 disabled making sure that UART1 is
fully software and hardware compatible with UARTs not equipped with this feature.
UART1 baudrate can be calculated as:
(4)
Where PCLK is the peripheral clock, U1DLM and U1DLL are the standard UART1 baud
rate divider registers, and DIVADDVAL and MULVAL are UART1 fractional baudrate
generator specific parameters.
The value of MULVAL and DIVADDVAL should comply to the following conditions:
1. 0 < MULVAL
≤
15
2. 0
≤
DIVADDVAL
≤
15
Table 116: UART1 Divisor Latch LSB register (U1DLL - address 0xE001 0000, when
DLAB = 1) bit description
Bit
Symbol
Description
Reset value
7:0
DLLSB
The UART1 Divisor Latch LSB Register, along with the U1DLM
register, determines the baud rate of the UART1.
0x01
Table 117: UART1 Divisor Latch MSB register (U1DLM - address 0xE001 0004, when
DLAB = 1) bit description
Bit
Symbol
Description
Reset value
7:0
DLMSB
The UART1 Divisor Latch MSB Register, along with the U1DLL
register, determines the baud rate of the UART1.
0x00
Table 118: UART1 Fractional Divider Register (U1FDR - address 0xE001 0028) bit description
Bit
Function
Description
Reset value
3:0
DIVADDVAL Baudrate generation pre-scaler divisor value. If this field is 0,
fractional baudrate generator will not impact the UART1
baudrate.
0
7:4
MULVAL
Baudrate pre-scaler multiplier value. This field must be greater
or equal 1 for UART1 to operate properly, regardless of
whether the fractional baudrate generator is used or not.
1
31:8
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA
UART1
baudrate
PCLK
16
16
U1DLM
×
U1DLL
+
(
)
×
1
DivAddVal
MulVal
-----------------------------
+
⎝
⎠
⎛
⎞
×
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