Interrupt Timer; Typical Pit Control Word Subroutine - Intel iSBC 86/14 Hardware Reference Manual

PROGRAMMING INFORMATION
a. Write counter register latch control word (Figure 3-3) to port OOD6.
The control word specifies the desired counter and selects the
counter latching operation.
b. Perform a read operation of the desired counter (refer to Table 3-3
for counter addresses).
NOTE
Be sure to read one or two bytes,
whichever was specified in the
initialization mode control word. For
two bytes, read in the order specified.
Table 3-5. Typical PIT Control Word Subroutine
INTTMR
INITIALIZ~S
COUNTERS 0,1,2. COUNTERS 0 AND 1 ARE INITIALIZED AS
INTERRUPT TIMERS. COUNTER 2 IS INITIALIZED AS A SQUARE WAVE GENERATOR.
ALL THREE COUNTERS ARE SET UP FOR 16-BIT OPERATION. DESTROYS-AL.
PUBLIC INTTMR
INTTMR:
MOV AL,30H jMODE CONTROL WORD FOR COUNTER 0 Mode O.
OUT OD6H,AL
MOV AL,7OH jMODE CONTROL WORD FOR COUNTER 1 Mode O.
OUT
OD6H,AL
MOV AL,B6H jMODE CONTROL WORD FOR COUNTER 2 Mode 1.
OUT OD6H,AL
RET
END
3-14