MC68HC08AZ16 Datasheet, PDF (295/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Programmable Interrupt Timer (PIT)
Functional Description
Figure 1 shows the structure of the PIT. The central component of the
PIT is the 16-bit PIT counter that can operate as a free-running counter
or a modulo up-counter. The counter provides the timing reference for
the interrupt. The PIT counter modulo registers, PMODH:PMODL, con-
trol the modulo value of the counter. Software can read the counter
value at any time without affecting the counting sequence.
INTERNAL
BUS CLOCK
PRESCALER
CSTOP
CRST
16-BIT COUNTER
16-BIT COMPARATOR
PITTMODH:PITTMODL
PRESCALER SELECT
PPS2 PPS1 PPS0
POF
PIE
Figure 1. PIT Block Diagram
INTERRUPT
LOGIC
Table 1. PIT I/O Register Summary
Register Name
Bit 7 6
5
4
3
2
1 Bit 0 Addr.
PITStatus/ControlRegister(PSC) POF PIE PSTOP PRST 0 PPS2 PPS1 PPS0 $004B
PITCounterRegister.High(PCNTH) Bit15 14 13 12 11 10
9
8 $004C
PITCounterRegister.Low(PCNTL) 7
6
5
4
3
2
1
0 $004D
PITCounterModuloReg.High(PMODH) Bit15 14 13 12 11 10
9
Bit8 $004E
PITCounterModuloReg.Low(PMODL) Bit7 6
5
4
3
2
1 Bit0 $004F
MC68HC08AZ32
294
Programmable Interrupt Timer (PIT)
2--pit
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