pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 167

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

Revision 1.07
Embedded Controller Modules
Timer and WATCHDOG Clock Pre-Scaler Register (TWCP)
The TWCP register is a byte-wide, read/write register. It defines the pre-scale ratio of the input clock and generates the T0IN
clock. On reset, the non-reserved bits of TWCP are initialized to 0.
Location: 00 FEE2
Type: R/W
TWD Timer 0 Register (TWDT0)
The TWDT0 register is a read/write register. It defines the T0OUT interrupt rate. On reset, this register is initialized to
FFFF
Location: 00 FEE4
Type: R/W
Bit
Name
Reset
Bit
Name
Reset
15-0 PRESET. Defines the counter preset value. Whenever the counter reaches zero, it starts counting down from
7-6
Bit
2-0
7-3
Bit
Bit
5
16
.
WDSDME. Selects the WATCHDOG touch mechanism
0: Disables the WATCHDOG service using WDSDM register. In this case, the WATCHDOG should be serviced
1: Selects the use of data match using the WDSDM mechanism.
Reserved.
MDIV. Defines the pre-scale ratio of the input clock. The pre-scale ratio is 2
the range of 0-5, providing a pre-scale ratio of 1 to 32.
MDIV allowed values:
Bits
2 1 0
0 0 0:
0 0 1:
0 1 0:
0 1 1:
1 0 0:
1 0 1:
Other
Reserved.
this value. The T0OUT frequency is the T0IN frequency divided by (PRESET+1). The allowed values of the
PRESET field are 0001
by writing a value to WDCNT register. When this bit is cleared, write operations to WDSDM are ignored.
15
1
16
16
Clock Ratio
1:1
1:2
1:4
1:8
1:16
1:32
Reserved
7
0
14
1
13
1
16
6
0
through FFFF
12
1
Reserved
11
1
(Continued)
5
0
16
10
1
.
9
1
Description
Description
Description
167
4
0
PRESET
8
1
7
1
3
0
6
1
5
1
MDIV
2
0
. The value of MDIV must be in
4
1
3
1
MDIV
1
0
2
1
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1
1
0
0
0
1