Sonic Alert msm83c154s, msm80154s user manual Counting control of timer/counters 0 and 1 by INT pin

MSM80C154S/83C154S/85C154HVS

M1

M1 or M2

S6

S1

S2

S3

S4

S5

S6

S1

S2

S3

S4

S5

S6

S1

S2

XTAL1

1

0

ALE

1

0

T0 or T1

1

COUNT IN

0

F/F1Q

1

0

F/F2Q

1

0

TIMER COUNT

1

0

Figure 4-9 Detector circuit operational time chart

4.5.2.4 Counting control of timer/counters 0 and 1 by INT pin

In addition to control by TR0 and TR1 bits of timer control register (TCON), timer/counter 0 and 1 counting start and stop can also be controlled by the signal level applied to the external interrupt pin in accordance with the GATE data values of bits 3 and 7 in the timer mode register (TMOD 89H) indicated in Table 4-9.

Timer/counter 0 is controlled by the bit 3, GATE bit. When the GATE bit is “0”, counting is started and stopped only by TR0.

When the GATE bit is “1”, counting in timer/counter 0 is enabled if the TR0 bit andINT0 pin input signal are both “1”. Counting is subsequently stopped if either is changed to “0” level. Timer/counter 1 is controlled by the bit 7, GATE bit, the functional operation being the same as timer/counter 0. The GATE - INT timer/counter counting control circuit is outlined in Figure 4-10, and the control table is given in Table 4-10.

Table 4-9 Timer mode register (TMOD 89H)

		Timer 1				Timer 0
Bit	7	6	5	4	3	2	1	0
Flag	GATE	C/T	M1	M0	GATE	C/T	M1	M0
Set	•				•

80