MC68HC08AS32A Datasheet, PDF (149/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Data Sheet — MC68HC08AS32A
Section 11. Programmable Interrupt Timer (PIT)
11.1 Introduction
This section describes the programmable interrupt timer (PIT) which is a periodic
interrupt timer whose counter is clocked internally via software programmable
options. Figure 11-1 is a block diagram of the PIT.
For further information regarding timers on M68HC08 Family devices, please
consult the HC08 Timer Reference Manual (Motorola document order number
TIM08RM/AD).
11.2 Features
Features of the PIT include:
• Programmable PIT clock input
• Free-running or modulo up-count operation
• PIT counter stop and reset bits
11.3 Functional Description
Figure 11-1 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, control 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
PRESCALER SELECT
PPS2 PPS1 PPS0
16-BIT COMPARATOR
TIMPMODH:TIMPMODL
Figure 11-1. PIT Block Diagram
POF
INTERRUPT
POIE
LOGIC
MC68HC08AS32A — Rev. 1
MOTOROLA
Programmable Interrupt Timer (PIT)
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
149