Freescale Semiconductor, Inc.
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.
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
CPE
CLK
POT2
POT1
POT0 MODE2 MODE1 MODE0
OC1
OC0
PCLK
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 TGATE≈.
Additionally, TOUTx can be used as a simple output 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
CPE
CLK
POT2
POT1
POT0 MODE2 MODE1 MODE0
OC1
OC0
PCLK
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.
8- 16
MC68340 USER’S MANUAL
MOTOROLA
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