Intel J1850 FH8065301455200 User Manual
Product codes
FH8065301455200
PCU - iLB - 8254 Timers
1226
Datasheet
26.6.4
TCW—Offset 43h
Timer Control Word Register. This register is programmed prior to any counter being
accessed to specify counter modes. Following 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.
Access Method
Default: 00h
26.6.5
C0AP—Offset 50h
Counter 0 Counter Access Port Register
Access Method
Default: 00h
Type: I/O Register
(Size: 8 bits)
TCW: 43h
7
4
0
0
0
0
0
0
0
0
0
CS
RWS
CM
S
BC
S
Bit
Range
Default &
Access
Description
7:6
X
WO
CS: Counter Select (CS): 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
5:4
X
WO
RWS: Read/Write Select RWS): The 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
3:1
X
WO
CMS: Counter Mode Selection (CMS): Selects one of six modes of operation for the
selected counter. 000 = Out signal on end of count (=0) 001 = Hardware retriggerable
one-shot x10 = Rate generator (divide by n counter) x11 = Square wave output 100 =
Software triggered strobe 101 = Hardware triggered strobe
0
X
WO
BCS: Binary/BCD Countdown Select (BCS): 0 Binary countdown is used. The largest
possible binary count is 216 1 Binary coded decimal (BCD) count is used. The largest
possible BCD count is 104
Type: I/O Register
(Size: 8 bits)
C0AP: 50h
7
4
0
0
0
0
0
0
0
0
0
CP
Bit
Range
Default &
Access
Description
7:0
X
RW
CP: Counter Port: Each counter port address is used to program the 16-bit Count
Register. The order of programming, either LSB only, MSB only, or LSB then MSB, is
defined with the Interval Counter Control Register at port 43h. The counter port is also
used to read the current count from the Count Register, and return the status of the
counter programming following a Read Back Command.