s908ab32ag0cfue Freescale Semiconductor, Inc, s908ab32ag0cfue Datasheet - Page 223

• Manufacturer Part Number: s908ab32ag0cfue
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

13.4.1 PIT Counter Prescaler
MC68HC908AB32
Freescale Semiconductor
Addr.
$004C
$004D
$004B
$004E
$004F
PIT Counter Register High
PIT Counter Register Low
PIT Status and Control
Register Name
PIT Counter Modulo
PIT Counter Modulo
Register High
Register Low
—
(PMODH)
(PMODL)
(PCNTH)
Rev. 1.1
(PCNTL)
Register
(PSC)
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 rolls over to $0000
after matching the value 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.
Reset:
Reset:
Reset:
Reset:
Reset:
Read:
Read:
Read:
Read:
Read:
Write:
Write:
Write:
Write:
Write:
Figure 13-2. PIT I/O Register Summary
Bit 15
Bit 15
Bit 7
POF
Bit 7
Bit 7
Programmable Interrupt Timer (PIT)
0
0
0
0
1
1
= Unimplemented
POIE
14
14
6
0
0
6
0
1
6
1
PSTOP
13
13
5
1
0
5
0
1
5
1
PRST
12
12
4
0
0
0
4
0
1
4
1
Programmable Interrupt Timer (PIT)
11
11
3
0
0
0
3
0
1
3
1
PPS2
10
10
2
0
0
2
0
1
2
1
PPS1
1
0
9
0
1
0
9
1
1
1
Technical Data
PPS0
Bit 0
Bit 8
Bit 0
Bit 8
Bit 0
0
0
0
1
1
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