ST92185B STMicroelectronics, ST92185B Datasheet - Page 16

• Manufacturer Part Number: ST92185B
• Description: 16k/24k/32k Rom Hcmos Mcu With On-screen-display
• Manufacturer: STMicroelectronics

ST92185B - GENERAL DESCRIPTION
PIN DESCRIPTION (Cont’d)
1.2.2 I/O Port Styles
Legend:
AF= Alternate Function, BID = Bidirectional, OD = Open Drain
PP = Push-Pull, TTL = TTL Standard Input Levels
How to Read this Table
To configure the I/O ports, use the information in
this table and the Port Bit Configuration Table in
the I/O Ports Chapter on
Port Style= the hardware characteristics fixed for
each port line.
Inputs:
– If port style = Standard I/O, either TTL or CMOS
– If port style = Schmitt trigger, selecting CMOS or
Weak Pull-Up = This column indicates if a weak
pull-up is present or not.
– If WPU = yes, then the WPU can be enabled/dis-
– If WPU = no, then enabling the WPU by software
Alternate Functions (AF) = More than one AF
cannot be assigned to an external pin at the same
time:
An alternate function can be selected as follows.
AF Inputs:
– AF is selected implicitly by enabling the corre-
AF Outputs or Bidirectional Lines:
– In the case of Outputs or I/Os, AF is selected
16/178
P0[7:0]
P2[5,4,3,2]
P2[1,0]
P3.7
P3[6,5,4]
P4[7:0]
P5[1:0]
input level can be selected by software.
TTL input by software has no effect, the input will
always be Schmitt Trigger.
able by software
has no effect
sponding peripheral. Exception to this are ADC
analog inputs which must be explicitly selected
as AF by software.
explicitly by software.
Pins
Weak Pull-Up
yes
no
no
no
no
no
no
page
69.
Schmitt trigger
Standard I/O
Standard I/O
Standard I/O
Standard I/O
Standard I/O
Standard I/O
Port Style
Example 1: ADC trigger digital input
AF: EXTRG, Port: P4.7, Port Style: Standard I/O.
Write the port configuration bits (for TTL level):
P4C2.7=1
P4C1.7=0
P4C0.7=1
Enable the ADC trigger by software as described
in the ADC chapter.
Example 2: PWM 0 output
AF: PWM0, Port: P4.0
Write the port configuration bits (for output push-
pull):
P4C2.0=0
P4C1.0=1
P4C0.0=1
Example 3: ADC analog input
AF: AIN1, Port : P2.1, Port style: does not apply to
analog inputs
Write the port configuration bits:
P2C2.1=1
P2C1.1=1
P2C0.1=1
BID / OD / TTL
BID / OD / TTL
BID / OD / TTL
BID / OD / TTL
BID / OD / TTL
BID / OD / TTL
Reset Values
AF / PP / TTL