8-BIT TIMER A/B
S3C8248/C8245/P8245/C8247/C8249/P8249
11-2
FUNCTION DESCRIPTION
Timer A Interrupts (IRQ0, Vectors E0H and E2H)
The timer A module can generate two interrupts: the timer A overflow interrupt (TAOVF), and the timer A match/
capture interrupt (TAINT). TAOVF is interrupt level IRQ0, vector E2H. TAINT also belongs to interrupt level
IRQ0, but is assigned the separate vector address, E0H.
Pending condition of timer A interrupts (overflow & match/capture) can be cleared automatically by hardware
where the interrupts are enabled. Otherwise pending condition must be cleared manually by software.
Interval Timer Function
The timer A module can generate an interrupt: the timer A match interrupt (TAINT). TAINT belongs to interrupt
level IRQ0, and is assigned the separate vector address, E0H.
When timer A match interrupt occurs and is serviced by the CPU, the pending condition is cleared automatically
by hardware.
In interval timer mode, a match signal is generated and TAOUT is toggled when the counter value is identical to
the value written to the TA reference data register, TADATA. The match signal generates a timer A match
interrupt (TAINT, vector E0H) and clears the counter.
If, for example, you write the value 10H to TADATA and 0AH to TACON, the counter will increment until it
reaches 10H. At this point, the TA interrupt request is generated, the counter value is reset, and counting
resumes.
Pulse Width Modulation Mode
Pulse width modulation (PWM) mode lets you program the width (duration) of the pulse that is output at the
TAPWM pin. As in interval timer mode, a match signal is generated when the counter value is identical to the
value written to the timer A data register. In PWM mode, however, the match signal does not clear the counter.
Instead, it runs continuously, overflowing at FFH, and then continues incrementing from 00H.
Although timer A overflow interrupt is occurred, this interrupt is not typically used in PWM-type applications.
Instead, the pulse at the TAPWM pin is held to Low level as long as the reference data value is less than or equal
to (
≤
) the counter value and then the pulse is held to High level for as long as the data value is greater than ( > )
the counter value. One pulse width is equal to t
CLK
• 256 .
Capture Mode
In capture mode, a signal edge that is detected at the TACAP pin opens a gate and loads the current counter
value into the TA data register. You can select rising or falling edges to trigger this operation.
Timer A also gives you capture input source: the signal edge at the TACAP pin. You select the capture input by
setting the value of the timer A capture input selection bit in the port 3 control register, P3CONL, (set 1, bank 0,
E9H). When P3CONL.7.6 is 00, the TACAP input or normal input is selected. When P3CONL.7.6 is set to 11,
normal output is selected.
Both kinds of timer A interrupts can be used in capture mode: the timer A overflow interrupt is generated
whenever a counter overflow occurs; the timer A match/capture interrupt is generated whenever the counter
value is loaded into the TA data register.
By reading the captured data value in TADATA, and assuming a specific value for the timer A clock frequency,
you can calculate the pulse width (duration) of the signal that is being input at the TACAP pin.
Содержание S3C8248
Страница 31: ...ADDRESS SPACES S3C8248 C8245 P8245 C8247 C8249 P8249 2 20 NOTES ...
Страница 107: ...INTERRUPT STRUCTURE S3C8248 C8245 P8245 C8247 C8249 P8249 5 18 NOTES ...
Страница 195: ...INSTRUCTION SET S3C8248 C8245 P8245 C8247 C8249 P8249 6 88 NOTES ...
Страница 221: ...I O PORTS S3C8248 C8245 P8245 C8247 C8249 P8249 9 16 NOTES ...
Страница 245: ...16 BIT TIMER 0 1 S3C8248 C8245 P8245 C8247 C8249 P8249 12 10 NOTES ...
Страница 249: ...WATCH TIMER S3C8248 C8245 P8245 C8247 C8249 P8249 13 4 NOTES ...
Страница 267: ...A D CONVERTER S3C8248 C8245 P8245 C8247 C8249 P8249 15 6 NOTES ...
Страница 299: ...S3P8245 P8249 OTP S3C8248 C8245 P8245 C8247 C8249 P8249 21 8 NOTES ...
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Страница 315: ...BOOK SPINE TEXT SAMSUNG Logo S3C8248 C8245 P8245 C8247 C8249 P8249 Microcontrollers User s Manual Rev 3 March 2002 ...