Motorola MC68340 用户手册
8- 16
MC68340 USER’S MANUAL
MOTOROLA
8.3.8 Timer Bypass
In this mode, the counter and prescaler cannot be enabled. However
TGATE
≈
and
TOUTx can be used for I/O. This mode can be selected by programming the CR MODE
bits to 111.
bits to 111.
TGATE
≈
can be used as a simple input port when the CR is configured as follows:
CR
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SWR
IE2
IE1
IE0
TGE
PCLK
CPE
CLK
POT2
POT1
POT0
MODE2 MODE1 MODE0
OC1
OC0
TGATE
≈
AS A SIMPLE INPUT
X
X
0
X
X
X
1
X
X
X
X
1
1
1
X
X
X-Don’t care
When
TGATE
≈
is asserted, the SR ON bit is set. When
TGATE
≈
is negated, the ON bit is
cleared. The value of the TGL bit in the SR reflects the level of
TGATE
≈
.
TGATE
≈
can
also be used as an input port that generates interrupts on a low-to-high transition of
TGATE
≈
when the CR is configured as follows:
CR
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SWR
IE2
IE1
IE0
TGE
PCLK
CPE
CLK
POT2
POT1
POT0
MODE2 MODE1 MODE0
OC1
OC0
TGATE
≈
AS AN INPUT/INTERRUPT
X
X
1
X
1
X
1
X
X
X
X
1
1
1
X
X
When
TGATE
≈
is negated, the SR TG bit is set, and the programmed
IRQx
signal is
asserted to the CPU32. The TG bit can only be cleared by writing a one to this bit position.
The value of the SR TGL bit reflects the level of
The value of the SR TGL bit reflects the level of
TGATE
≈
.
Additionally, TOUTx can be used as a simple output port when the CR is configured as
follows:
follows:
CR
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SWR
IE2
IE1
IE0
TGE
PCLK
CPE
CLK
POT2
POT1
POT0
MODE2 MODE1 MODE0
OC1
OC0
TGATE
≈
AS A SIMPLE OUTPUT
0
X
X
X
X
X
1
X
X
X
X
1
1
1
OC1
OC0
SWR must be a zero to change the value of TOUTx. Changing the value of the CR OCx
bits determines the level of TOUTx as shown in Table 8-1.
bits determines the level of TOUTx as shown in Table 8-1.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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