MC68HC11A1 MOTOROLA [Motorola, Inc], MC68HC11A1 Datasheet - Page 38

• Manufacturer Part Number: MC68HC11A1
• Description: 8-Bit Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

9 Pulse Accumulator
38
MCU PIN
MOTOROLA
(FROM MAIN TIMER)
PA7/
PAI/
OC1
E
The MC68HC11A8 has an 8-bit counter that can be configured to operate as a simple event counter or
for gated time accumulation, depending on the PAMOD bit in the PACTL register. The pulse accumu-
lator counter can be read or written at any time.
The port A bit 7 I/O pin can be configured as a clock in event counting mode, or as a gate signal to en-
able a free-running clock (E divided by 64) in gated time accumulation mode.
MAIN TIMER
64 CLOCK
Pulse Accumulator (in Gated Mode)
FROM
Cycle Time
CPU Clock
OC1
(E/2
(E/2
DDRA7
FROM
14
6
)
)
OUTPUT
BUFFER
EDGE DETECTOR
INPUT BUFFER
AND
Figure 12 Pulse Accumulator System Block Diagram
Selected Crystal
TMSK2 INT ENABLES
PACTL CONTROL
overflow —
1 count —
Table 9 Pulse Accumulator Timing
(1/E)
(E)
DATA
BUS
MUX
2
:
1
16.384 ms
4.0 MHz
1.0 MHz
1000 ns
64.0 s
CLOCK
PAI EDGE
PAEN
PAEN
INTERNAL
DATA BUS
Common XTAL Frequencies
TFLG2 INTERRUPT STATUS
ENABLE
OVERFLOW
8.192 ms
8.0 MHz
2.0 MHz
32.0 s
500 ns
PACNT 8-BIT COUNTER
PAOVI
PAOVF
PAII
PAIF
DISABLE
FLAG SETTING
MC68HC11A8TS/D
MC68HC11A8
12.0 MHz
5.461 ms
21.33 s
3.0 MHz
333 ns
PULSE ACC BLOCK
INTERRUPT
REQUESTS
1
2