
CTM
REFERENCE
MOTOROLA
8-3
DOUBLE ACTION SUBMODULE (DASM)
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8
8.2
32-bit coherent access
In the IPWM and IPM modes, 32-bit coherent access of the data registers is supported (see
Section 1.3.4). 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.
8.3
DASM modes of operation
The mode of operation of the DASM is determined by the mode select bits MODE[3:0] in the
DASMSIC register (see Table 8-1).
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
4. Re-enable DASM interrupts (if desired)
Note:
When changing between output modes (OP, OC or OCT), it is not necessary to follow
this procedure, as in these modes the FLAG bit merely indicates to the software that
the compare value can be updated.
Table 8-1
DASM modes of operation
MODE[3:0]
0000
Mode
DIS
Description of mode
Disabled — Input pin is high impedance; IN gives state of the input pin.
Input pulse width measurement — Capture on the leading edge and the
trailing edge of an input pulse.
Input period measurement — Capture two consecutive rising/falling edges.
Input capture — Capture when the designated edge is detected.
Output compare, flag set on B compare — Generate leading and trailing
edges of an output pulse and set the flag.
Output compare, flag on A and B compare — Generate leading and trailing
edges of an output pulse and set the flag.
Output pulse width modulation — Generate continuous PWMoutput with 7,
9, 11, 12, 13, 14, 15 or 16 bits of resolution.
0001
IPWM
0010
0011
IPM
IC
0100
OCB
0101
OCAB
1xxx
OPWM
F
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