MC68336/376
CONFIGURABLE TIMER MODULE 4
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
10-10
the requested interrupt designated by IL[2:0] to determine whether it should contend
for arbitration priority. During arbitration, the BIUSM provides the arbitration value
specified by IARB[2:0] in BIUMCR and IARB3 in MCSMSIC. If the CTM4 wins arbitra-
tion, it responds with a vector number generated by concatenating VECT[7:6] in
BIUMCR and the six low-order bits specified by the number of the submodule request-
ing service. Thus, for MCSM12 in CTM4, six low-order bits would be 12 in decimal, or
%001100 in binary.
10.7.7 MCSM Registers
The MCSM contains a status/interrupt/control register, a counter, and a modulus latch.
All unused bits and reserved address locations return zero when read. Writes to
unused bits and reserved address locations have no effect. The CTM4 contains three
Latch Registers for information concerning MCSM register and bit descriptions.
10.8 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
input 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 reset by the other one. Interrupt requests can optionally be generated by the input
capture 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 10-2 shows the different
DASM operating modes.