MC68HC05RC17 Datasheet, PDF (80/128 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
Carrier Modulator Transmitter (CMT)
9.5.3 Extended Space Operation
In either time or FSK mode, the space period can be made longer than
the maximum possible value of SBUFF. Setting the EXSPC bit in the
MCSR will force the modulator to treat the next modulation period
(beginning with the next load of MBUFF/SBUFF) 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 EXSPC will return the modulator to
standard operation at the beginning of the next modulation period. To
calculate the length of an extended space in time mode, use the
equation:
t_exspace =
((SBUFF₁)+(MBUFF₂+1+SBUFF₂) +... (MBUFF_n+1+SBUFF_n)) x 8 _secs
f_osc
Where the subscripts 1, 2, ... n refer to the modulation periods that
elapsed while the EXSPC bit was set.
Similarly, to calculate the length of an extended space in FSK mode, use
the equation:
t_exspace =
((SBUFF₁)+(MBUFF₂+1+SBUFF₂)+... (MBUFF_n+1+SBUFF_n))_secs
f_cg
Where f_cg is the frequency output from the carrier generator. For an
example of extended space operation, see Figure 9-6.
NOTE: The EXSPC feature can be used to emulate a zero mark event.
SET EXSPC
CLEAR EXSPC
Figure 9-6. Extended Space Operation
General Release Specification
MC68HC05RC17 — Rev. 2.0
Carrier Modulator Transmitter (CMT)
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