Information

• Secondary carrier high count = 0x03
• Secondary carrier low count = 0x01
IRO signal
Modulator gate
Carrier out (fcg)
Mark1
Space1
Mark2
Space2
Mark1
Mark2
Space1
Figure 40-18. Example: CMT output in FSK mode
40.7.4 Extended space operation
In either Time, Baseband, or FSK mode, the space period can be made longer than the
maximum possible value of the space period register. Setting MSC[EXSPC] will force
the modulator to treat the next modulation period beginning with the next load of the
counter and space period register, as a space period equal in length to the mark and space
counts combined. Subsequent modulation periods will consist entirely of these extended
space periods with no mark periods. Clearing MSC[EXSPC] will return the modulator to
standard operation at the beginning of the next modulation period.
40.7.4.1 EXSPC operation in Time mode
To calculate the length of an extended space in Time or Baseband mode, add the mark
and space times and multiply by the number of modulation periods when MSC[EXSPC]
is set.
t
exspace
= (t
mark
+ t
space
) * (number of modulation periods)
For an example of extended space operation, see Figure 40-19.
Note
The extended space enable feature can be used to emulate a
zero mark event.
Chapter 40 Carrier Modulator Transmitter (CMT)
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
Freescale Semiconductor, Inc.
Preliminary
1007
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