Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
8
2
SECTION 10
16-BIT TIMER
3
4
10.1 Introduction
5
The MC68HC805P18 MCU contains a single 16-bit programmable timer with an
input capture function and an output compare function. The 16-bit timer is driven
by the output of a fixed divide-by-four prescaler operating from the PH2 clock. The
16-bit timer may be used for many applications including input waveform
measurement, while simultaneously generating an output waveform. Pulse widths
can vary from microseconds to seconds depending on the oscillator frequency
selected. The 16-bit timer is also capable of generating periodic interrupts. See
Figure 10-1.
6
7
8
Because the timer has a 16-bit architecture, each function is represented by two
registers. Each register pair contains the high and low byte of that function.
Generally, accessing the low byte of a specific timer function allows full control of
that function; however, an access of the high byte inhibits that specific timer
function until the low byte is also accessed.
9
10
11
12
13
14
A
NOTE
The I bit in the condition code register (CCR) should be set while
manipulating both the high and low byte registers of a specific timer
function. This prevents interrupts from occurring between the time
the high and low bytes are accessed.
16
17
18
19
20
16-BIT TIMER
Rev. 1.0
For More Information On This Product,
Go to: www.freescale.com
FREESCALE [ Freescale ]
