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I/O ports
ST7LITEUS2, ST7LITEUS5
9.6
I/O port implementation
The hardware implementation on each I/O port depends on the settings in the DDR and OR
registers and specific feature of the I/O port such as ADC Input or true open drain.
Switching these I/O ports from one state to another should be done in a sequence that
prevents unwanted side effects. Recommended safe transitions are illustrated in
Other transitions are potentially risky and should be avoided, since they are likely to present
unwanted side-effects such as spurious interrupt generation.
Figure 29.
Interrupt I/O port state transitions
The I/O port register configurations are summarized in
After reset, to configure PA3 as a general purpose output, the application has to program
the MUXCR0 and MUXCR1 registers. See
Section 6.5: Register description on page 37
Table 22.
Port configuration
Port
Pin name
Input (DDR=0)
Output (DDR=1)
OR = 0
OR = 1
OR = 0
OR = 1
Port A
PA0:2,
PA4:5
floating
pull-up interrupt
open drain
push-pull
PA3
-
-
open drain
push-pull
Table 23.
I/O port register map and reset values
Address
(Hex.)
Register
label
7
6
5
4
3
2
1
0
0000h
PADR
Reset
value
MSB
0
0
0
0
0
0
0
LSB
0
0001h
PADDR
Reset
value
MSB
0
0
0
0
1
0
0
LSB
0
0002h
PAOR
Reset
value
MSB
0
0
0
0
0
0
1
LSB
0
01
floating/pull-up
interrupt
INPUT
00
floating
(reset state)
INPUT
10
open-drain
OUTPUT
11
push-pull
OUTPUT
XX
= DDR, OR
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