Samsung KS57C2308 manual TC0 Counter Register TCNT0, TC0 Timing Diagram

KS57C2308/P2308/C2316/P2316 TIMERS and TIMER/COUNTERS

TC0 COUNTER REGISTER (TCNT0)

The 8-bit counter register for timer/counter 0, TCNT0, is read-only and can be addressed by 8-bit RAM control instructions. RESET sets all TCNT0 register values to logic zero (00H).

Whenever TMOD0.3 is enabled, TCNT0 is cleared to logic zero and counting resumes. TCNT0 register value is incremented at the selected edge each time an incoming pulse with reference clock specified by TMOD0 register (specifically, TMOD0.6, TMOD0.5, and TMOD0.4) is input.

Each time TCNT0 is incremented, the new value is compared with the reference value stored in the TC0 reference buffer, TREF0. When TCNT0 = TREF0, an match signal occurs in the comparator, the interrupt request flag, IRQT0, is set to logic one, and an interrupt request is generated to indicate that the specified timer/counter interval has elapsed.

COUNT

CLOCK

~

~

TREF0

REFERENCE VALUE = n

~

~

TCNT0

0

1

2

n-1

n

0

1

2

n-1

n

0

1

2

3

~

~

MATCH

MATCH

~

TOL0

~

INTERVAL TIME

TIMER START INSTRUCTION

IRQT0 SET

IRQT0 SET

(TMOD0.3 IS SET)

Figure 11-3. TC0 Timing Diagram

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