C167CR
C167SR
Direct Drive
When direct drive is configured (CLKCFG = 011B) the on-chip phase locked loop is
disabled and the CPU clock is directly driven from the internal oscillator with the input
clock signal.
The frequency of fCPU directly follows the frequency of fOSC so the high and low time of
f
CPU (i.e. the duration of an individual TCL) is defined by the duty cycle of the input clock
fOSC
.
The timings listed below that refer to TCLs therefore must be calculated using the
minimum TCL that is possible under the respective circumstances. This minimum value
can be calculated via the following formula:
TCLmin = 1/fOSC × DCmin
(DC = duty cycle)
For two consecutive TCLs the deviation caused by the duty cycle of fOSC is compensated
so the duration of 2TCL is always 1/fOSC. The minimum value TCLmin therefore has to
be used only once for timings that require an odd number of TCLs (1, 3, …). Timings that
require an even number of TCLs (2, 4, …) may use the formula 2TCL = 1/fOSC
.
Data Sheet
52
V3.2, 2001-07
INFINEON [ Infineon ]
