ACE1001MT8X_32 View Datasheet(PDF) - Fairchild Semiconductor

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ACE1001MT8X_32

Arithmetic Controller Engine (ACEx™) for Low Power Applications

Fairchild Semiconductor 

5.0 Timer 1

Timer 1 is a versatile 8-bit timer. Its main function is to operate as

a Pulse Width Modulation (PWM) generator that generates pulses

of a specified width and duty cycles.

Timer 1 contains an 8-bit timer register (TMR1), an 8-bit auto-

reload register (T1RA), and an 8-bit control register (T1CNTRL).

All registers are memory-mapped for simple access through the

core. For the PWM signal generation the timer contains an output

(T1) that is multiplexed with the I/O pin G2.

The timer can be started or stopped through the T1CNTRL

register bit T1C0. When running, the timer counts down (decre-

ments) every clock cycle. The timer’s clock has a pre-scalar and

is selectable through two T1CNTRL register bits T1PSC[1:0].

Depending on the selected operating mode, occurrences of timer

underflow (transitions from 0x00 to 0xFF or reload) can either

generate an interrupt and/or toggle the T1 output pin.

Timer 1’s interrupt (TMRI1) can be enabled by the interrupt enable

(T1EN) bit in the T1CNTRL register. When the timer interrupt is

enabled, the source of the interrupt is a timer underflow. By

default, the timer register is reset to 0xFF and the auto-reload

register is reset to 0x00.

5.1 Timer control bits

Reading and writing to the T1CNTRL register controls the timer’s

operation. By writing to the control bits, the user can enable or

disable the timer interrupts, set the mode of operation, start or stop

the timer, and select the clock. The T1CNTRL register bits are

described in Table 12.

Table 12: TIMER1 Control Register Bits

T1CNTRL Register

Bit 7

Bit 6

Bit 5

Name

-----------

-----------

T1C1

Bit 4

Bit 3

T1C0

T1PND

Bit 2

T1EN

Bit 1,0

T1PSC

Function

Reserved

Reserved

T1 toggle enable bit: 1 = T1 toggle enabled, 0 = T1 toggle

disabled

TMR1 run: 1 = Start timer, 0 = Stop timer

Timer1 interrupt pending flag: 1 = Timer1 interrupt

pending, 0 = Timer1 interrupt not pending

Timer1 interrupt enable bit: 1 = Timer1 interrupt enabled,

0 = Timer1 interrupt disabled

Pre-scalar selection bits: Selects the 1MHz clock divider to be

by 1 (00b), 2 (01b), 4 (10b), or 8 (11b)

19

ACE1001 Product Family Rev. B.1

www.fairchildsemi.com

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