MC68HC11L1VFB View Datasheet(PDF) - Freescale Semiconductor
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MC68HC11L1VFB Datasheet PDF : 124 Pages
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Freescale Semiconductor, Inc.
PR[1:0] — Timer Prescaler Select
These bits are used to select the prescaler divide-by ratio. In normal modes, PR[1:0]
can only be written once, and the write must be within 64 cycles after reset. Refer to
Table 9-1 for specific timing values.
PR[1:0]
00
01
10
11
Prescaler
1
4
8
16
9.3.10 Timer Interrupt Flag 2 Register
Bits in this register indicate when certain timer system events have occurred. Coupled
with the four high-order bits of TMSK2, the bits of TFLG2 allow the timer subsystem to
operate in either a polled or interrupt driven system. Each bit of TFLG2 corresponds
to a bit in TMSK2 in the same position.
TFLG2 — Timer Interrupt Flag 2
Bit 7
6
5
4
3
2
TOF
RTIF
PAOVF
PAIF
0
0
RESET:
0
0
0
0
0
0
Clear flags by writing a one to the corresponding bit position(s).
$0025
1
Bit 0
0
0
0
0
TOF — Timer Overflow Interrupt Flag
Set when TCNT changes from $FFFF to $0000
RTIF — Real-Time (Periodic) Interrupt Flag
Refer to 9.4 Real-Time Interrupt.
PAOVF — Pulse Accumulator Overflow Interrupt Flag
Refer to 9.6 Pulse Accumulator.
PAIF — Pulse Accumulator Input Edge Interrupt Flag
Refer to 9.6 Pulse Accumulator.
Bits [3:0]— Not implemented
Always read zero
9.4 Real-Time Interrupt
The real-time interrupt feature, used to generate hardware interrupts at a fixed periodic
rate, is controlled and configured by two bits (RTR1 and RTR0) in the pulse accumu-
lator control (PACTL) register. The RTII bit in the TMSK2 register enables the interrupt
capability. The four different rates available are a product of the MCU oscillator fre-
quency and the value of bits RTR[1:0]. Refer to the following table, which shows the
periodic real-time interrupt rates.
9-12
TIMING SYSTEM
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