Information

38.7.4 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.
38.7.4.1 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 38-19.
Note
The extended space enable feature can be used to emulate a
zero mark event.
Set EXSPC
Clear EXSPC
Figure 38-19. Extended space operation
38.7.4.2 EXSPC operation in FSK mode
In FSK mode, the modulator continues to count carrier out clocks, alternating between
the primary and secondary registers at the end of each modulation period.
To calculate the length of an extended space in FSK mode, it is required to know whether
MSC[EXSPC] was set on a primary or secondary modulation period, and the total
number of both primary and secondary modulation periods completed while
MSC[EXSPC] is high. A status bit for the current modulation is not accessible to the
Functional description
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
862 Freescale Semiconductor, Inc.