NH82801DB S L8DE Intel, NH82801DB S L8DE Datasheet - Page 321

• Manufacturer Part Number: NH82801DB S L8DE
• Manufacturer: Intel

Specifications of NH82801DB S L8DE

• Lead Free Status / RoHS Status: Compliant

9.3
9.3.1
Intel
®
82801DB ICH4 Datasheet
Timer I/O Registers
TCW—Timer Control Word Register
I/O Address:
Attribute:
This register is programmed prior to any counter being accessed to specify counter modes.
Following part reset, the control words for each register are undefined and each counter output is 0.
Each timer must be programmed to bring it into a known state.
There are two special commands that can be issued to the counters through this register, the Read
Back Command and the Counter Latch Command. When these commands are chosen, several bits
within this register are redefined. These register formats are described below.
Port
40h
41h
42h
43h
Bit
7:6
5:4
3:1
0
Counter Select — WO. The Counter Selection bits select the counter the control word acts upon as
shown below. The Read Back Command is selected when bits[7:6] are both 1.
00 = Counter 0 select
01 = Counter 1 select
10 = Counter 2 select
11 = Read Back Command
Read/Write Select — WO. These bits are the read/write control bits. The actual counter
programming is done through the counter port (40h for counter 0, 41h for counter 1, and 42h for
counter 2).
00 = Counter Latch Command
01 = Read/Write Least Significant Byte (LSB)
10 = Read/Write Most Significant Byte (MSB)
11 = Read/Write LSB then MSB
Counter Mode Selection — WO. These bits select one of six possible modes of operation for the
selected counter.
000 = Mode 0Out signal on end of count (=0)
001 = Mode 1Hardware retriggerable one-shot
x10 = Mode 2Rate generator (divide by n counter)
x11 = Mode 3Square wave output
100 = Mode 4Software triggered strobe
101 = Mode 5Hardware triggered strobe
Binary/BCD Countdown Select — WO.
0 = Binary countdown is used. The largest possible binary count is 2 16
1 = Binary coded decimal (BCD) count is used. The largest possible BCD count is 10 4
Aliases
50h
51h
52h
53h
43h
WO
Counter 0 Interval Time Status Byte Format
Counter 0 Counter Access Port Register
Counter 1 Interval Time Status Byte Format
Counter 1 Counter Access Port Register
Counter 2 Interval Time Status Byte Format
Counter 2 Counter Access Port Register
Timer Control Word Register
Timer Control Word Register Read Back
Counter Latch Command
Register Name/Function
Description
Default Value:
Size:
LPC Interface Bridge Registers (D31:F0)
Default Value
0XXXXXXXb
0XXXXXXXb
0XXXXXXXb
XXXXXXX0b
Undefined
Undefined
Undefined
Undefined
X0h
All bits undefined
8 bits
Type
R/W
R/W
R/W
WO
WO
WO
RO
RO
RO
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