ST90158 - GENERAL DESCRIPTION
1.3 I/O PORT PINS
All the ports of the device can be programmed as
Input/Output or in Input mode, compatible with
TTL or CMOS levels (except where Schmitt Trig-
ger is present). Each bit can be programmed indi-
vidually (Refer to the I/O ports chapter).
Push-Pull/OD Output
The output buffer can be programmed as push-
pull or open-drain: attention must be paid to the
fact that the open-drain option corresponds only to
a disabling of P-channel MOS transistor of the
buffer itself: it is still present and physically con-
nected to the pin. Consequently it is not possible to
increase the output voltage on the pin over
TTL/CMOS Input
For all those port bits where no input schmitt trig-
ger is implemented, it is always possible to pro-
gram the input level as TTL or CMOS compatible
by programming the relevant PxC2.n control bit.
Refer to the section titled “Input/Output Bit Config-
uration” in the I/O Ports Chapter .
V
+0.3 Volt, to avoid direct junction biasing.
DD
Table 1. I/O Port Characteristics
Input
Output
Weak Pull-Up Reset State
Port 0
Port 1
Port 2
Port 4
Port 5
Port 6
Port 7
Port 8
Port 9
TTL/CMOS
TTL/CMOS
TTL/CMOS
Schmitt trigger
Schmitt trigger
TTL/CMOS
Schmitt trigger
Schmitt trigger
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Yes
Yes
No
Bidirectional WPU
Bidirectional WPU
Bidirectional
Yes
Yes
No
Bidirectional WPU
Bidirectional WPU
Bidirectional
Yes
Yes
Yes
Bidirectional WPU
Bidirectional WPU
Bidirectional WPU
Legend: WPU = Weak Pull-Up, OD = Open Drain
13/199
9
ETC [ ETC ]
