MC68HC08AS32A Datasheet, PDF (150/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Programmable Interrupt Timer (PIT)
Addr.
Register Name
Bit 7
6
5
4
3
PIT Status and Control ^{Read: POF}
POIE PSTOP
0
0
$004B
Register (PSC) Write: 0
PRST
See page 152. _Reset:
0
0
1
0
0
PIT Counter Register High ^{Read: Bit 15}
14
13
12
11
$004C
(PCNTH) Write:
See page 153. _Reset:
0
0
0
0
0
PIT Counter Register Low ^{Read: Bit 7}
6
5
4
3
$004D
(PCNTL) Write:
See page 153. _Reset:
0
0
0
0
0
PIT Counter Modulo ^Read: _{Bit 15}
14
13
12
11
$004E Register High (PMODH) Write:
See page 154. _Reset:
1
1
1
1
1
PIT Counter Modulo ^Read: _{Bit 7}
6
5
4
3
$004F Register Low (PMODL) Write:
See page 154. _Reset:
1
1
1
1
1
=Unimplemented
Figure 11-2. PIT I/O Register Summary
2
PPS2
0
10
0
2
0
10
1
2
1
1
PPS1
0
9
0
1
0
9
1
1
1
Bit 0
PPS0
0
Bit 8
0
Bit 0
0
Bit 8
1
Bit 0
1
11.4 PIT Counter Prescaler
The clock source can be one of the seven prescaler outputs. The prescaler
generates seven clock rates from the internal bus clock. The prescaler select bits,
PPS[2:0], in the status and control register select the PIT clock source.
The value in the PIT counter modulo registers and the selected prescaler output
determines the frequency of the periodic interrupt. The PIT overflow flag (POF) is
set when the PIT counter value reaches the modulo value programmed in the PIT
counter modulo registers. The PIT interrupt enable bit, POIE, enables PIT overflow
CPU interrupt requests. POF and POIE are in the PIT status and control register.
11.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby
modes.
11.5.1 Wait Mode
The PIT remains active after the execution of a WAIT instruction. In wait mode the
PIT registers are not accessible by the CPU. Any enabled CPU interrupt request
from the PIT can bring the MCU out of wait mode.
If PIT functions are not required during wait mode, reduce power consumption by
stopping the PIT before executing the WAIT instruction.
Data Sheet
150
Programmable Interrupt Timer (PIT)
For More Information On This Product,
Go to: www.freescale.com
MC68HC08AS32A — Rev. 1
MOTOROLA