Information

Carrier out

(fcg)

Modulator gate

IRO signal

(Time mode)

IRO signal

(Baseband mode)

Mark

Space

Mark

CMTCLK 8

Figure 38-17. Example: CMT output in Time and Baseband modes with OC[CMTPOL]=0

38.7.3.2 Baseband mode

Baseband mode, that is, when MSC[MCGEN] and MSC[BASE] 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 38-17 for an example of the

output for both Baseband and Time modes. In the example, the carrier out frequency (f

)

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.

Note

The waveforms in Figure 38-17 and Figure 38-18 are for the

purpose of conceptual illustration and are not meant to

represent precise timing relationships between the signals

shown.

38.7.3.3 FSK mode

When the modulator operates in FSK mode, that is, when MSC[MCGEN] and

MSC[FSK] are set, and MSC[BASE] is cleared:

Functional description

K20 Sub-Family Reference Manual, Rev. 2, Feb 2012

858 Freescale Semiconductor, Inc.