Motorola MPC533 Reference Manual page 752

MIOS14 Double Action Submodule (MDASM)
In the disable mode (DIS) and in the input modes, the PIN bit reflects the state present on
the input signal (after being Schmitt triggered and synchronized). In the output modes the
PIN bit reflects the value present on the output flip-flop. The output flip-flop is used in
output modes to hold the logic level applied to the output signal.
The 16-bit counter bus selector is common to all input and output functions; it connects the
MDASM to one of the four 16-bit counter buses available to that submodule instance and
is controlled in software by the 16-bit counter bus selector bits BSL0 and BSL1 in the
MDASMSCR register.
17.9.3 MDASM Modes of Operation
The mode of operation of the MDASM is determined by the mode select bits MODE[0:3]
in the MDASMSCR register (see Table 17-17).
MODE[0:3] Mode
0000 DIS Disabled — Input signal is high impedance; PIN gives state of the input signal.
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 line activated on B compare — Generate leading and trailing edges of an output
pulse.
0101 OCAB Output compare, flag line activated on A and B compare — Generate leading and trailing edges of an
output pulse.
1xxx OPWM Output pulse width modulation — Generate continuous PWM output with 7, 9, 11, 12, 13, 14, 15 or 16
bits of resolution.
To avoid spurious interrupts, and to make sure that the FLAG line is activated according to
the newly selected mode, the following sequence of operations should be adopted when
changing mode:
1. Disable MDASM interrupts (by resetting the enable bit in the relevant MIRSM)
2. Change mode (via disable mode)
3. Reset the corresponding FLAG bit in the relevant MIRSM
4. Re-enable MDASM interrupts (if desired)
When changing between output modes, 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. However changing modes without passing via the
disable mode does not guarantee the subsequent functionality.
17-28
Table 17-17. MDASM Modes of Operation
MPC533 Reference Manual
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Description of Mode
NOTE
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