MC68332
TIME PROCESSOR UNIT
USER’S MANUAL
7-13
Figure 7-3 TCR2 Prescaler Control
When the T2CG bit is set, the external TCR2 pin functions as a gate of the DIV8 clock
(the TPU system clock divided by 8). In this case, when the external TCR2 pin is low,
the DIV8 clock is blocked, preventing it from incrementing TCR2. When the external
TCR2 pin is high, TCR2 is incremented at the frequency of the DIV8 clock. When
T2CG is cleared, an external clock from the TCR2 pin, which has been synchronized
and fed through a digital filter, increments TCR2.
The TCR2 field in TPUMCR specifies the value of the prescaler: 1, 2, 4, or 8. Channels
using TCR2 have the capability to resolve down to the TPU system clock divided by
is a summary of prescaler output.
7.6.1.3 Emulation Control
Asserting the EMU bit in the TPUMCR places the TPU in emulation mode. In emula-
tion mode, the TPU executes microinstructions from TPURAM exclusively. Access to
the TPURAM module through the IMB by a host is blocked, and the TPURAM module
is dedicated for use by the TPU. After reset, EMU can be written only once.
7.6.1.4 Low-Power Stop Control
If the STOP bit in the TPUMCR is set, the TPU shuts down its internal clocks, shutting
down the internal microengine. TCR1 and TCR2 cease to increment and retain the last
value before the stop condition was entered. The TPU asserts the stop flag (STF) in
the TPUMCR to indicate that it has stopped.
Table 7-2 TCR2 Prescaler Control
TCR2 Prescaler
Divide By
Internal Clock
Divided By
External Clock
Divided By
00
1
8
1
01
2
16
2
10
4
32
4
11
8
64
8
PRESCALER CTL BLOCK 2
DIGITAL
FILTER
EXTERNAL
TCR2 PIN
TCR2
(T2CG CONTROL BIT)
0 – A
1 – B
0
15
A
B
MUX
CONTROL
SYNCHRONIZER
TCR2
PRESCALER
00
÷
1
01
÷
2
10
÷
4
11
÷
8
INT CLK /8
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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