
Coppertail Product Specification
MT8LLN22NCNE.fm – Rev. 1, Pub. 2/02
76
2002, Micron Technology Inc.
PRELIMINARY
MT8LLN22NCNE
COPPERTAIL
Timer/Counter I/O Register Set
The I/O Controller contains three timer/counters
that are equivalent in function to those found in one
8254 programmable interval timer. These three
counters are used to provide system timer functions
and speaker tone for the PC buzzer. The 14.31818-MHz
oscillator input provides the clock source for these
three counters. 
Table 9 summarizes the Timer/
Counter I/O register set.
Counter Access Port Register
Table 9
Timer Counter I/O Register Set
ADDRESS
ALIAS
REGISTER
0040h
0050h
Counter 0 Timer Access Port.
Counter 0 Timer Status.
0041h
0051h
Counter 1 Timer Access Port.
Counter 1 Timer Status.
0042h
0052h
Counter 2 Timer Access Port.
Counter 2 Timer Status.
0043h
0053h
Timer Control Word.
Read Back Command.
Counter Latch Command.
ADDRESS: 40h
ADDRESS: 41h
ADDRESS: 42h
COUNTER 0
COUNTER 1
COUNTER 2
BITS
DESCRIPTION
PROPERTIES
RESET
7:0
The Counter Access Port is used to program the 8-bit or 16-bit Count reg-
ister. The Interval Counter Control register at 43h controls the specific
byte of information read or written. The Access port may also be used to
read the current count from the Count register, read the Latched Count,
or return status following a READ BACK command.
R/W
00
Interval Timer Status Byte Format Register
ADDRESS: 40h
SYMBOL: SBYTE_FMT
ADDRESS: 41h
ADDRESS: 42h
COUNTER 0
COUNTER 1
COUNTER 2
BITS
DESCRIPTION
PROPERTIES
RESET
7
Counter Out Pin State. Returns the Out pin state.
W/O
N/A
6
Count Register Status. When set, indicates the count has not yet been
loaded and is not yet available for reading. When clear, indicates the
count has been transferred from the Count Register to the Counting Ele-
ment and is available for reading.
W/O
N/A
5:4
Read/Write Control Status.
00: Counter Latch Command. See definition below.
01: Access Least Significant Byte (LSB).
10: Access Most Significant Byte (MSB).
11: Access LSB then MSB.
W/O
00b