MPC555
/
MPC556
TIME PROCESSOR UNIT 3
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
17-6
— If the standard prescaler is selected (EPSCKE = 0), the the PSCK bit deter-
mines whether the standard prescaler divides the IMB clock input by 32 (PSCK
= 0) or four (PSCK = 1)
— If the enhanced prescaler is selected (EPSCKE = 1), the EPSCK bits select a
value by which the IMB clock is divided. The lowest frequency for TCR1 clock
is IMB clock divided by 64x8. The highest frequency for TCR1 clock is IMB
clock divided by two (2x1). See
— The output of either the standard prescaler or the enhanced prescaler is then
divided by 1, 2, 4, or 8, depending on the value of the TCR1P field in the
TPUMCR.
— If the DIV2 bit is one, the TCR1 counter increments at a rate of the internal
clock divided by two. If DIV2 is zero, the TCR1 increment rate is defined by the
output of the TCR1 prescaler (which, in turn, takes as input the output of either
the standard or enhanced prescaler).
shows a diagram of the TCR1 prescaler control block.
Table 17-1 Enhanced TCR1 Prescaler Divide Values
EPSCK Value
Divide IMB Clock By
0x00
2
0x01
4
0x02
6
0x03
8
0x04, 0x05,...0x1d
10,12,...60
0x1e
62
0x1f
64
Table 17-2 TCR1 Prescaler Values
TCR1P Value
Divide by
0b00
1
0b01
2
0b10
4
0b11
8
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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