CP3BT26 Datasheet, PDF (202/278 Pages) National Semiconductor (TI) – Reprogrammable Connectivity Processor with Bluetooth-R, USB, and CAN Interfaces

26.3 TIMER INTERRUPTS
26.4 TIMER I/O FUNCTIONS
The 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 77 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.
The Multi-Function Timer unit uses two I/O pins, called TA
and TB. The function of each pin depends on the timer op-
erating mode and the TAEN and TBEN enable bits. Table 78
shows the functions of the pins 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, 3, or 4 (in other
words, when TCRA is not used in Capture mode).
Table 77 Timer Interrupts Overview
Sys. Int.
Interrupt
Pending
Bit
Timer
Int. 1
(TA Int.)
TAPND
TBPND
TCPND
Timer TDPND
Int. 2
(TB Int.)
Mode 1
PWM + Counter
TCNT1 reload from
TCRA
TCNT1 reload from
TCRB
N/A
TCNT2 underflow
Mode 2
Mode 3
Dual Input Capture +
Counter
Dual Counter
Input capture on TA
transition
Input Capture on TB
transition
TCNT1 underflow
TCNT2 underflow
TCNT1 reload from
TCRA
N/A
N/A
TCNT2 reload from
TCRB
Mode 4
Single Capture +
Counter
TCNT1 reload from
TCRA
Input Capture on TB
transition
N/A
TCNT2 underflow
I/O
TAEN
TBEN
TA TAEN = 0
TBEN = X
TAEN = 1
TBEN = X
TB TAEN = X
TBEN = 0
TAEN = X
TBEN = 1
Table 78 Timer I/O Functions
Mode 1
Mode 2
Mode 3
PWM + Counter
Dual Input Capture +
counter
Dual Counter
No Output
Capture TCNT1 into
TCRA
Toggle Output on Capture TCNT1 into
Underflow of TCNT1 TCRA and Preset
TCNT1
Ext. Event or Pulse Capture TCNT1 into
Accumulate Input TCRB
Ext. Event or Pulse
Accumulate Input
Capture TCNT1 into
TCRB and Preset
TCNT1
No Output Toggle
Toggle Output on
Underflow of TCNT1
Ext. Event or Pulse
Accumulate Input
Ext. Event or Pulse
Accumulate Input
Mode 4
Single Capture +
counter
No Output Toggle
Toggle Output on
Underflow of TCNT1
Capture TCNT2 into
TCRB
Capture TCNT2 into
TCRB and Preset
TCNT2
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