Information

Table 40-1. Modes of operation (continued)
Modes Description
Frequency-shift key
This mode allows the carrier generator to alternate between
two sets of high and low times. When operating in FSK
mode, the generator will toggle between the two sets when
instructed by the modulator, allowing the user to
dynamically switch between two carrier frequencies without
CPU intervention.
The following table summarizes the modes of operation of the CMT module.
Table 40-2. CMT modes of operation
Mode MSC[MCGEN]
1
MSC[BASE]
2
MSC[FSK]
2
MSC[EXSPC] Comment
Time 1 0 0 0
f
cg
controlled by primary high and
low registers.
f
cg
transmitted to the IRO signal
when modulator gate is open.
Baseband 1 1 X 0
f
cg
is always high. The IRO signal is
high when the modulator gate is
open.
FSK 1 0 1 0
f
cg
control alternates between
primary high/low registers and
secondary high/low registers.
f
cg
transmitted to the IRO signal
when modulator gate is open.
Extended
Space
1 X X 1
Setting MSC[EXSPC] causes
subsequent modulator cycles to be
spaces (modulator out not asserted)
for the duration of the modulator
period (mark and space times).
IRO Latch 0 X X X
OC[IROL] controls the state of the
IRO signal.
1. To prevent spurious operation, initialize all data and control registers before beginning a transmission when
MSC[MCGEN]=1.
2. This field is not double-buffered and must not be changed during a transmission while MSC[MCGEN]=1.
NOTE
The assignment of module modes to core modes is chip-
specific. For module-to-core mode assignments, see the chapter
that describes how modules are configured.
40.4.1 Wait mode operation
During Wait mode, the CMT if enabled, will continue to operate normally. However,
there is no change in operating modes of CMT during Wait mode, because the CPU is not
operating.
Modes of operation
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
988
Preliminary
Freescale Semiconductor, Inc.
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