Information

t
mark
= (CMD1:CMD2 + 1) ÷ (f
CMTCLK
÷ 8)
t
space
= CMD3:CMD4 ÷ (f
CMTCLK
÷ 8)
where CMD1:CMD2 and CMD3:CMD4 are the decimal values of the concatenated
registers.
C A R R IE R O U T
( f
cg
)
M O D U L A T O R G A T E
IRO SIGNAL (TIME MODE)
IRO SIGNAL
(BASEBAND MODE)
MARK
SPACE
MARK
CMTCLK 8
Figure 40-17. Example: CMT Output in Time and Baseband Modes with OC[CMTPOL]=0
40.7.3.2 Baseband Mode
Baseband mode (MSC[MCGEN] and MSC[BASE] bits are set) is a derivative of time
mode, where the mark and space period is based on (CMTCLK ÷ 8) counts. The mark
and space calculations are the same as in time mode. In this mode, the modulator output
will be at a logic 1 for the duration of the mark period and at a logic 0 for the duration of
a space period. See Figure 40-17 for an example of the output for both baseband and time
modes. In the example, the carrier out frequency (f
cg
) is generated with a high count of
0x01 and a low count of 0x02 that results in a divide of 3 of CMTCLK with a 33% duty
cycle. The modulator down counter was loaded with the value 0x0003 and the space
period register with 0x0002.
Functional Description
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
1024 Freescale Semiconductor, Inc.