CP3BT10 Datasheet, PDF (148/210 Pages) National Semiconductor (TI) – Reprogrammable Connectivity Processor with Bluetooth and USB Interfaces

23.3 TIMER INTERRUPTS
23.4 TIMER I/O FUNCTIONS
Each Multi-Function Timer unit has four interrupt sources,
designated A, B, C, and D. Interrupt sources A, B, and C are
mapped into a single system interrupt called Timer Interrupt
1, while interrupt source D is mapped into a system interrupt
called Timer Interrupt 2. Each of the four interrupt sources
has its own enable bit and pending bit. The enable bits are
named TAIEN, TBIEN, TCIEN, and TDIEN. The pending
bits are named TAPND, TBPND, TCPND, and TDPND.
Timer Interrupts 1 and 2 are system interrupts TA and TB
(IRQ14 and IRQ13), respectively.
Table 52 shows the functions of the TA pin in each operating
mode, and for each combination of enable bit settings.
When the TA pin is configured to operate as a PWM output
(TAEN = 1), the state of the pin is toggled on each underflow
of the TCNT1 counter. In this case, the initial value on the
pin is determined by the TAOUT bit. For example, to start
with TA high, software must set the TAOUT bit before en-
abling the timer clock. This option is available only when the
timer is configured to operate in Mode 1 or 3 (in other words,
when TCRA is not used in Capture mode).
Table 51 shows the events that trigger interrupts A, B, C,
and D in each of the four operating modes. Note that some
interrupt sources are not used in some operating modes.
Table 51 Timer Interrupts Overview
Sys. Int.
Interrupt
Pending
Bit
Timer
Int. 1
(TA Int.)
TAPND
TBPND
Timer
Int. 2
(TB Int.)
TCPND
TDPND
Mode 1
Mode 2
Mode 3
PWM + Counter
Dual Input Capture +
Counter
Dual Counter
TCNT1 reload from TCRA Input capture on TA transition TCNT1 reload from TCRA
TCNT1 reload from TCRB Input Capture on TB
N/A
transition
N/A
TCNT1 underflow
N/A
TCNT2 underflow
TCNT2 underflow
TCNT2 reload from TCRB
I/O
TAEN
TBEN
TA
TAEN = 0
TBEN = X
TAEN = 1
TBEN = X
Table 52 Timer I/O Functions
Mode 1
Mode 2
Mode 3
PWM + Counter
No Output
Dual Input Capture +
counter
Capture TCNT1 into TCRA
Dual Counter
No Output Toggle
Toggle Output on
Underflow of TCNT1
Capture TCNT1 into TCRA Toggle Output on Underflow
and Preset TCNT1
of TCNT1
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