MOTOROLA
12-12
CONFIGURABLE TIMER MODULE 7
MC68HC16R1/916R1
USER’S MANUAL
12.8.2 SASM Registers
The SASM contains one status/interrupt/control register and two data registers (A and
B). All unused bits and reserved address locations return zero when read. Writes to
unused bits and reserved address locations have no effect. The CTM7 contains six
SASMs, each with its own set of registers. Refer to
D.7.14 SASM Status/Interrupt/
Control Registers
and
D.7.15 SASM Data Registers
for information concerning
SASM register and bit descriptions.
12.9 Double-Action Submodule (DASM)
The double-action submodule (DASM) allows two 16-bit input capture or two 16-bit
output compare functions to occur automatically without software intervention. The in-
put edge detector can be programmed to trigger the capture function on user-specified
edges. The output flip flop can be set by one of the output compare functions, and re-
set by the other one. Interrupt requests can optionally be generated by the input cap-
ture and the output compare functions. The user can select one of two incoming time
bases for the input capture and output compare functions.
Six operating modes allow the DASM input capture and output compare functions to
perform pulse width measurement, period measurement, single pulse generation, and
continuous pulse width modulation, as well as standard input capture and output com-
pare. The DASM can also function as a single I/O pin.
DASM operating mode is determined by the mode select field (MODE[3:0]) in the
DASM status/interrupt/control register (DASMSIC).
Table 12-3
shows the different
DASM operating modes.
The DASM is composed of two timing channels (A and B), an output flip-flop, an input
edge detector, some control logic and an interrupt interface. All control and status bits
are contained in DASMSIC.
Table 12-3 DASM Modes of Operation
MODE[3:0]
0000
Mode
DIS
Description of Mode
Disabled — Input pin is high impedance; IN gives state of input pin
Input pulse width measurement — Capture on 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 set on A and B compare — Generate leading and trailing
edges of an output pulse and set the flag
Reserved
Reserved
Output pulse width modulation — Generate continuous PWM output with 7, 9, 11,
12, 13, 14, 15, or 16 bits of resolution
0001
IPWM
0010
0011
IPM
IC
0100
OCB
0101
OCAB
0110
0111
—
—
1xxx
OPWM