mc68hc908rc24d Freescale Semiconductor, Inc, mc68hc908rc24d Datasheet - Page 130

• Manufacturer Part Number: mc68hc908rc24d
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Carrier Modulator Transmitter (CMT)
12.6.3 FSK Mode
Advance Information
130
When the modulator operates in FSK mode, the modulation mark and
space periods consist of an integer number of carrier clocks (space
period can be 0). When the mark period expires, the space period is
transparently started (as in time mode). The carrier generator toggles
between primary and secondary data register values whenever the
modulator space period expires.
The space period provides an interpulse gap (no carrier). If SBUFF = 0,
then the modulator and carrier generator will switch between carrier
frequencies without a gap or any carrier glitches (0 space).
Using timing data for carrier burst and interpulse gap length calculated
by the CPU, FSK mode can automatically generate a phase-coherent,
dual-frequency FSK signal with programmable burst and interburst
gaps.
The mark and space time equations for FSK mode are:
Where f
CG
Carrier Modulator Transmitter (CMT)
t mark
t space
is the frequency output from the carrier generator.
=
MBUFF
-------------------------------
=
SBUFF
-------------------- -
f CG
f CG
+
1
sec
sec
s
s
MC68HC908RC24 — Rev. 1.1
Freescale Semiconductor