MC68HC11F1 Datasheet, PDF (64/68 Pages) Motorola, Inc – Technical Summary 8-Bit Microcontroller

13 Pulse Accumulator
The pulse accumulator can be used either to count events or measure the duration of a particular event.
In event counting mode, the pulse accumulator’s 8-bit counter increments each time a specified edge
is detected on the pulse accumulator input pin, PA7. The maximum clocking rate for this mode is the E-
clock divided by two. In gated time accumulation mode, an internal clock increments the 8-bit counter
at a rate of E-clock ÷ 64 while the input at PA7 remains at a predetermined logic level.
13.1 Pulse Accumulator Block Diagram
1
INTERRUPT
REQUESTS
2
TMSK2
INTERRUPT ENABLES
E ÷ 64 CLOCK
(FROM MAIN TIMER)
PA7/
PAI/OC1
INPUT BUFFER
&
EDGE DETECTION
OUTPUT
BUFFER
FROM
MAIN TIMER
OC1
FROM
DDRA
2:1
MUX
PACTL
CONTROL
PAI EDGE
PAEN
CLOCK
PAEN
TFLG2
STATUS FLAGS
OVERFLOW
PACNT
8-BIT COUNTER
ENABLE
INTERNAL
DATA BUS
Figure 18 Pulse Accumulator Block Diagram
13.2 Pulse Accumulator Registers
TMSK2 — Timer Interrupt Mask 2
Bit 7
6
5
4
3
TOI
RTII
PAOVI
PAII
0
RESET:
0
0
0
0
0
$x024
2
1
Bit 0
0
PR1
PR0
0
0
0
Bits [7:4] in TMSK2 correspond bit for bit with flag bits in TFLG2. Setting any of these bits enables the
corresponding interrupt source.
MOTOROLA
64
MC68HC11F1/FC0
MC68HC11FTS/D