TMP03/TMP04

REV. A

–12–

Listing 1. An 80C51 Software Routine for the TMP04

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Test of a TMP04 interface to the 8051,

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using timer 0 and timer 1 to measure the duty cycle

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This program has three steps:

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1. Clear the timer registers, then wait for a low-to-

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high transition on input P1.0 (which is connected

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to the output of the TMP04).

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2. When P1.0 goes high, timer 0 starts. The program

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then loops, testing P1.0.

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3. When P1.0 goes low, timer 0 stops & timer 1 starts. The

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program loops until P1.0 goes low, when timer 1 stops

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and the TMP04’s T1 and T2 values are stored in Special

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Function registers 8AH through 8DH (TL0 through TH1).

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Primary controls

$MOD51

$TITLE(TMP04 Interface, Using T0 and T1)

$PAGEWIDTH(80)

$DEBUG

$OBJECT

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Variable declarations

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PORT1

DATA

90H

;SFR register for port 1

;TCON

DATA

88H

;timer control

;TMOD

DATA

89H

;timer mode

;TH0

DATA

8CH

;timer 0 hi byte

;TH1

DATA

8DH

;timer 1 hi byte

;TL0

DATA

8AH

;timer 0 lo byte

;TL1

DATA

8BH

;timer 1 low byte

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ORG

100H

;arbitrary start

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READ_TMP04:

MOV

A,#00

;clear the

MOV

TH0,A

; counters

MOV

TH1,A

;

first

MOV

TL0,A

;

MOV

TL1,A

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WAIT_LO:

JB

PORT1.0,WAIT_LO

;wait for TMP04 output to go low

MOV

A,#11H

;get ready to start timer0

MOV

TMOD,A

WAIT_HI:

JNB

PORT1.0,WAIT_HI

;wait for output to go high

;

;Timer 0 runs while TMP04 output is high

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SETB

TCON.4

;start timer 0

WAITTIMER0:

JB

PORT1.0,WAITTIMER0

CLR

TCON.4

;shut off timer 0

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;Timer 1 runs while TMP04 output is low

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SETB

TCON.6

;start timer 1

WAITTIMER1:

JNB

PORT1.0,WAITTIMER1

CLR

TCON.6

;stop timer 1

MOV

A,#0H

;get ready to disable timers

MOV

TMOD,A

RET

END

Software for the interface is shown in Listing 1. The program

monitors the TMP04 output, and turns the counters on and off

to measure the duty cycle. The time that the output is high is mea-

sured by Timer 0, and the time that the output is low is measured

by Timer 1. When the routine finishes, the results are available

in Special Function Registers (SFRs) 08AH through 08DH.