MC68F375
CONFIGURABLE TIMER MODULE (CTM9)
MOTOROLA
REFERENCE MANUAL
Rev. 25 June 03
13-25
In the disabled mode (DIS) and in the input modes, the IN bit reflects the state present
on the input pin (after being Schmitt triggered and synchronized). In the output modes
the IN bit reflects the value present at the output of the output flip-flop. The output flip-
flop is used in output modes to hold the logic level applied to the output pin.
The time base bus selector is common to all input and output functions; it connects the
DASM to time base bus A or B and is controlled in software by the bus select bit BSL
in the DASMSIC register.
13.5.1 32-Bit Coherent Access
In the IPWM and IPM modes, 32-bit coherent access of the data registers is sup-
ported. A 32-bit coherent access consists of doing a long word aligned access of data
register A. In this case, register A is accessed first, immediately followed (on the next
cycle) by a register B access. During this time, any flag setting or data transfer from
the hidden B register is deferred until coherent access has ended. When the 32-bit
access has ended, the DASM finishes any pending B action and resumes normal
operation.
13.5.2 DASM Modes of Operation
The mode of operation of the DASM is determined by the mode select bits MODE[3:0]
WARNING
To avoid spurious interrupts, and to make sure that the FLAG bit is
set according to the newly selected mode, the following sequence of
operations should be adopted when changing mode:
1. Disable DASM interrupts
2. Change mode
3. Reset the corresponding FLAG bit
Table 13-8 DASM Modes of Operation
MODE[3:0]
Mode
Description of mode
0000
DIS
Disabled — Input pin is high impedance; IN gives state of the input pin.
0001
IPWM
Input pulse width measurement — Capture on the leading edge and the trailing edge of
an input pulse.
0010
IPM
Input period measurement — Capture two consecutive rising/falling edges.
0011
IC
Input capture — Capture when the designated edge is detected.
0100
OCB
Output compare, flag set on B compare — Generate leading and trailing edges of an out-
put pulse and set the flag.
0101
OCAB
Output compare, flag on A and B compare — Generate leading and trailing edges of an
output pulse and set the flag.
1xxx
OPWM
Output pulse width modulation — Generate continuous PWM output with 7, 9, 11, 12,
13, 14, 15 or 16 bits of resolution.
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Freescale Semiconductor, Inc.
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