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8-BIT TIMER A/B S3C8245/P8245/C8249/P8249
11-10
F PROGRAMMING TIP — To generate a one pulse signal through P3.0
This example sets Timer B to the one shot mode, sets the oscillation frequency as the Timer B clock source, and
TBDATAH and TBDATAL to make a 40 µs width pulse. The program parameters are:
40
µ
s
— Timer B is used in one shot mode
— Oscillation frequency is 4 MHz (1 clock = 0.25 µs)
— TBDATAH = 40 µs / 0.25 µs = 160, TBDATAL = 1
— Set P3.0 to TBPWM mode
ORG 0100H ; Reset address
START DI
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LD TBDATAH,# (160-2) ; Set 40 µs
LD TBDATAL,# 1 ; Set any value except 00H
LD TBCON,#00000001B ; Clock Source ← f
OSC
; Disable Timer B interrupt.
; Select one shot mode for Timer B.
; Stop Timer B operation.
; Set Timer B output flip-flop (TBOF) high
LD P3CONL, #02H ; Set P3.0 to TBPWM mode.
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Pulse_out: LD TBCON,#00000101B ; Start Timer B operation
; to make the pulse at this point.
• ; After the instruction is executed, 0.75 µs is required
• ; before the falling edge of the pulse starts.
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