I/O ports
ST92124xxx-Auto/150xxxxx-Auto/250xxxx-Auto
Table 5. I/O port characteristics (continued)
Port
Input
Output
Port 3[2:0] (1)
Port 3.3
Port 3[7:4]
Schmitt trigger
TTL/CMOS
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Port 4.0, Port 4.4
Port 4.1
Port 4.2, Port 4.5
Port 4.3
Port 4[7:6]
Schmitt trigger
Schmitt trigger
TTL/CMOS
Schmitt trigger
High hysteresis Schmitt
trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Pure OD
Port 5[2:0], Port
5[7:4]
Port 5.3
Schmitt trigger
TTL/CMOS
Push-Pull/OD
Push-Pull/OD
Port 6[3:0]
Port 6[5:4]
Port 6[7:6] (1)
Schmitt trigger
High hysteresis Schmitt
trigger
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Port 7[7:0]
Schmitt trigger
Push-Pull/OD
Port 8[1:0]
Port 8[7:2]
Schmitt trigger
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Port 9[7:0]
Schmitt trigger
Push-Pull/OD
1. Port 3.0 and Port6 [7:6] present on ST92250-Auto version only.
Weak pull-up Reset state
Yes
Input
Yes
Input CMOS
Yes
Input
No
Yes
Yes
Yes
No
Input
Bidirectional
WPU
Input CMOS
Input
Input
No
Input
Yes
Input CMOS
Yes
Input
Yes
Input
Yes
Input
Yes
Input
Yes
Yes
Input
Bidirectional
WPU
Yes
Bidirectional
WPU
Legend: WPU = Weak Pull-Up, OD = Open Drain.
How to configure the I/O ports
To configure the I/O ports, use the information in Table 5, Table and the Port Bit
Configuration Table in Section 13: I/O ports
Input Note = the hardware characteristics fixed for each port line in Table 5.
● If Input note = TTL/CMOS, either TTL or CMOS input level can be selected by software.
● If Input note = Schmitt trigger, selecting CMOS or TTL input by software has no effect,
the input will always be Schmitt Trigger.
Alternate Functions (AF) = More than one AF cannot be assigned to an I/O pin at the
same time:
An alternate function can be selected as follows.
AF Inputs:
● AF is selected implicitly by enabling the corresponding peripheral. Exception to this are
ADC inputs which must be explicitly selected as AF input by software.
AF Outputs or Bidirectional Lines:
● In the case of Outputs or I/Os, AF is selected explicitly by software.
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Doc ID 13898 Rev 2