MC68340 datasheet(374/441 Pages) FREESCALE

374 / 441 page

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MC68340 USER’S MANUAL

MOTOROLA

* Timer1 register offsets from timer1 base address

IR1

EQU $604

interrupt register timer1

CR1

EQU $606

control register timer1

SR1

EQU $608

status register timer1

CNTR1

EQU $60A

counter register timer1

COM1

EQU $610

compare register timer1

***************************************************************************

* Initialize Timer1

***************************************************************************

LEA

MODBASE+TIMER1,A0

Pointer to timer1 module

* Disable timer1

CLR.W

CR1(A0)

* Allow TGATE to negate and assert so that an accurate count will result.

* If SR1 TGL bit=1, continue looping. TGATE is negated.

LOOP1

BTST.B

#$3,SR1(A0)

BNE.B

LOOP1

* If TGL bit=0, continue looping. TGATE is asserted.

LOOP2

BTST.B

#$3,SR1(A0)

BEQ.B

LOOP2

* Ready to initialize timer1, TGATE is negated.

* Module configuration register:

* Timer1 module is set for normal operation, ignore FREEZE.

* Supervisor/user timer1 registers unrestricted.

* Interrupt arbitration at priority $03.

MOVE.W

#$0003,MCR1(A0)

* Initialize timer1 interrupt level to 2 and vector to $0F

MOVE.W

#$020F,IR1(A0)

* Initialize the compare register to 0

CLR.W

COM1(A0)

* Clear the SR1 TG bit (by writing a 1) to use as a flag

MOVE.B

#$20,SR1(A0)

* Control register 1:

* Enable timer1, no interrupts are enabled, TGATE signal used to control

* the counter. Use the selected clock for the counter clock, and enable it.

* Selected clock is 1/2 system's freq. Pulse-width measurement,

* disable TOUT.

Freescale Semiconductor, Inc.

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MC68340 Datasheet(PDF) 374 Page - Freescale Semiconductor, Inc

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