cp3ub17 National Semiconductor Corporation, cp3ub17 Datasheet - Page 141

• Manufacturer Part Number: cp3ub17
• Description: Reprogrammable Connectivity Processor With Usb Interface
• Manufacturer: National Semiconductor Corporation

22.3
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 48 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.
Timer
Int. 1
(TA Int.)
Timer
Int. 2
(TB Int.)
TA
Sys. Int.
I/O
TIMER INTERRUPTS
TAEN = 0
TBEN = X
TAEN = 1
TBEN = X
TAPND
TBPND
TCPND
TDPND
Interrupt
Pending
TBEN
TAEN
Bit
TCNT1 reload from TCRA Input capture on TA transition TCNT1 reload from TCRA
TCNT1 reload from TCRB Input Capture on TB
N/A
TCNT2 underflow
No Output
Toggle Output on
Underflow of TCNT1
PWM + Counter
PWM + Counter
Table 48 Timer Interrupts Overview
Mode 1
Mode 1
Table 49 Timer I/O Functions
141
transition
TCNT1 underflow
TCNT2 underflow
Capture TCNT1 into TCRA
Capture TCNT1 into TCRA
and Preset TCNT1
22.4
Table 49 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).
Dual Input Capture +
Dual Input Capture +
Counter
counter
Mode 2
Mode 2
TIMER I/O FUNCTIONS
N/A
N/A
TCNT2 reload from TCRB
No Output Toggle
Toggle Output on Underflow
of TCNT1
Dual Counter
Dual Counter
Mode 3
Mode 3
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