MOTOROLA
Chapter 17. Modular Input/Output Subsystem (MIOS14)
17-45
MIOS14 Double Action Submodule (MDASM)
3—
Reserved
4
EDPOL
Polarity bit — In the DIS mode, this bit is not used; reading it returns the last value written.
In the IPWM mode, this bit is used to select the capture edge sensitivity of channels A and B.
1 Channel A captures on a falling edge. Channel B captures on a rising edge.
0 Channel A captures on a rising edge. Channel B captures on a falling edge.
In the IPM and IC modes, the EDPOL bit is used to select the input capture edge sensitivity of
channel A.
1 Channel A captures on a falling edge.
0 Channel A captures on a rising edge.
In the OCB, OCAB and OPWM modes, the EDPOL bit is used to select the voltage level on the
output signal. If open-drain mode is selected via the WOR bit, the EDPOL bit is disabled and
writing to it will have no effect on the output voltage.
1 The complement of the output flip-flop logic level appears on the output signal: a match on
channel A resets the output signal; a match on channel B sets the output signal.
0 The output flip-flop logic level appears on the output signal: a match on channel A sets the
output signal, a match on channel B resets the output signal.
The EDPOL bit is cleared by reset.
5
FORCA
Force A bit — In the OCB, OCAB and OPWM modes, the FORCA bit allows the software to force
the output flip-flop to behave as if a successful comparison had occurred on channel A (except
that the FLAG line is not activated). Writing a one to FORCA sets the output flip-flop; writing a
zero to it has no effect.
In the DIS, IPWM, IPM and IC modes, the FORCA bit is not used and writing to it has no effect.
FORCA is cleared by reset and is always read as zero.
Writing a one to both FORCA and FORCB simultaneously resets the output flip-flop.
6
FORCB
Force B bit — In the OCB, OCAB and OPWM modes, the FORCB bit allows the software to force
the output flip-flop to behave as if a successful comparison had occurred on channel B (except
that the FLAG line is not activated). Writing a one to FORCB resets the output flip-flop; writing a
zero to it has no effect.
In the DIS, IPWM, IPM and IC modes, the FORCB bit is not used and writing to it has no effect.
FORCB is cleared by reset and is always read as zero.
Writing a one to both FORCA and FORCB simultaneously resets the output flip-flop.
7:8
—
Reserved
9:10
BSL
Bus select bits — These bits are used to select which of the six 16-bit counter buses is used by
the MDASM. Each MDASM instance has four possible counter buses that may be connected.
NOTE: Unconnected counter buses inputs are grounded.
11
—
Reserved
12:15
MODE
Mode select bits — The four mode select bits select the mode of operation of the MDASM. To
avoid spurious interrupts, it is recommended that MDASM interrupts are disabled before
changing the operating mode.
The mode select bits are cleared by reset.
NOTE: The reserved modes should not be set; if these modes are set, the MDASM behavior is
undefined.
Table 17-21. MDASMSCR Bit Descriptions (continued)
Bits
Name
Description