MC68HC12 Datasheet, PDF (263/478 Pages) Motorola, Inc – The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit

Enhanced Capture Timer
Timer Register Descriptions
PAIF — Pulse Accumulator Input edge Flag
Set when the selected edge is detected at the PT7 input pin. In event
mode the event edge triggers PAIF and in gated time accumulation
mode the trailing edge of the gate signal at the PT7 input pin triggers
PAIF.
This bit is cleared by a write to the PAFLG register with bit 0 set.
Any access to the PACN3, PACN2 registers will clear all the flags in
this register when TFFCA bit in register TSCR($86) is set.
PACN3, PACN2 — Pulse Accumulators Count Registers
$00A2, $00A3
BIT 7
6
5
4
3
2
1
BIT 0
$00A2
BIt 7
6
5
4
3
2
1
Bit 0 PACN3 (hi)
$00A3
Bit 7
6
5
4
3
2
1
Bit 0 PACN2 (lo)
RESET:
0
0
0
0
0
0
0
0
Read or write any time.
The two 8-bit pulse accumulators PAC3 and PAC2 are cascaded to form
the PACA 16-bit pulse accumulator. When PACA in enabled (PAEN=1
in PACTL, $A0) the PACN3 and PACN2 registers contents are
respectively the high and low byte of the PACA.
When PACN3 overflows from $FF to $00, the Interrupt flag PAOVF in
PAFLG ($A1) is set.
Full count register access should take place in one clock cycle. A
separate read/write for high byte and low byte will give a different result
than accessing them as a word.
PACN1, PACN0 — Pulse Accumulators Count Registers
$00A4, $00A5
BIT 7
6
5
4
3
2
1
BIT 0
$00A4
BIt 7
6
5
4
3
2
1
Bit 0 PACN1 (hi)
$00A5
Bit 7
6
5
4
3
2
1
Bit 0 PACN0 (lo)
RESET:
0
0
0
0
0
0
0
0
Read or write any time.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Enhanced Capture Timer
Technical Data
263