GMS77C1001 datasheet(29/44 Pages) HYNIX

29 / 44 page

GMS77C1000/GMS77C1001

July. 2001 Ver. 1.1

11.1 Timer Mode

If the OPTION register bit5(T0CS) is cleared, the timer

mode is selected and is operated with internal system clock

(TCY). The Timer0 module will increment every instruc-

tion cycle (without prescaler). If TMR0 register is written,

the increment is inhibited for the following two cycles. The

user can work around this by writing an adjusted value to

the TMR0 register.

Figure 11-3 and Figure 11-4 show the timing diagram of

Timer.

- No Prescaler (PSA=0)

Timer will increment every instruction cycle(Q4).

- With Prescaler (PSA=1)

Timer will increment with prescaler division ratio.

@ PS2~PS0 = (1:2) ~ (1:256)Counter Mode

11.2 Counter Mode

If the OPTION register bit5(T0CS) is set, the counter

mode is selected and operates with event clock input.

In this mode, Timer0 will increment either on every rising

or falling edge of pin EC0. The incrementing edge is deter-

mined by the source edge select bit T0SE (OPTION<4>).

Clearing the T0SE bit selects the rising edge.

FIGURE 11-3 TIMER0 TIMING: INTERNAL CLOCK/NO PRESCALE

FIGURE 11-4 TIMER0 TIMING: INTERNAL CLOCK/PRESCALER 1:2

[ W ’ TMR0 ]

PC-1

TMR0

Instruction

Fetch

Q1 Q2 Q3 Q4

PC+1

Q1 Q2 Q3 Q4

PC+2

Q1 Q2 Q3 Q4

PC+3

Q1 Q2 Q3 Q4

PC+4

Q1 Q2 Q3 Q4

PC+5

Q1 Q2 Q3 Q4

PC+6

Q1 Q2 Q3 Q4

[ TMR0 ’ W ]

T0+1

T0+2

NT0

NT0+1

NT0+2

Write TMR0

executed

Read TMR0

reads NT0

Read TMR0

reads NT0

Read TMR0

reads NT0

Read TMR0

reads NT0+1

Read TMR0

reads NT0+2

(Program

Counter)

Instruction

Executed

increment inhibited

Timer0

Clock

[ W ’ TMR0 ]

PC-1

TMR0

Instruction

Fetch

Q1 Q2 Q3 Q4

PC+1

Q1 Q2 Q3 Q4

PC+2

Q1 Q2 Q3 Q4

PC+3

Q1 Q2 Q3 Q4

PC+4

Q1 Q2 Q3 Q4

PC+5

Q1 Q2 Q3 Q4

PC+6

Q1 Q2 Q3 Q4

[ TMR0 ’ W ]

T0+1

NT0

NT0+1

(Program

Counter)

increment inhabited

Timer0

Clock

Write TMR0

executed

Read TMR0

reads NT0

Read TMR0

reads NT0

Read TMR0

reads NT0

Read TMR0

reads NT0+1

Read TMR0

reads NT0+2

Instruction

Executed

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