Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 8- 21
IE2–IE0—Interrupt Enable
These bits determine which sources of interrupts, TO, TG, and TC, are enabled to
generate an interrupt request to the CPU32. Table 8-3 lists which interrupts are enabled
for all bit combinations.
Table 8-3. IEx Encoding
IE2 IE1 IE0 Enabled Interrupts
0 0 0 Polling Mode (No Interrupts Enabled)
0 0 1 TC Enabled
0 1 0 TG Enabled
0 1 1 TG and TC Enabled
1 0 0 TO Enabled
1 0 1 TO and TC Enabled
1 1 0 TO and TG Enabled
1 1 1 TO, TG, and TC Enabled
TGE—Timing Gate Enable
1 = The
TGATE≈ signal is enabled to control the enabling and disabling of the
prescaler and counter, except in the input capture/output compare mode (see
8.3.1 Input Capture/Output Compare).
0 = The
TGATE≈ signal has no effect on the timer operation.
PCLK—Prescaler Clock Select
This bit selects which clock is used for the counter clock.
1 = The counter is decremented by the prescaler output tap as selected by the POT
field in the CR.
0 = The counter is decremented by the selected clock.
The prescaler continues to decrement regardless of how PCLK is set.
CPE—Counter Prescaler Enable
1 = The selected clock is enabled. If the TGE bit is set, then
TGATE≈ must also be
asserted (except in the input capture/output compare mode).
0 = The selected clock is held high, halting the prescaler and counter.
CLK—Clock
1 = The selected clock is taken from the TINx input.
0 = The selected clock is one-half the system clock's frequency.
The TOUTx of one timer can be fed externally into the TINx input of the other timer,
resulting in a 32-bit counter if the prescalers are not used and a 48-bit counter if they
are used.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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