ST92195B - GENERAL INFORMATION
1.2.2 I/O Port Styles
Pins | Weak | Port Style | Reset Values |
P0[7:0] | no | Standard I/O | BID / OD / TTL |
P2[5,4,3,2] | no | Standard I/O | BID / OD / TTL |
P2[1,0] | no | Schmitt trigger | BID / OD / TTL |
P3.7 | yes | Standard I/O | AF / PP / TTL |
P3[6,5,4] | no | Standard I/O | BID / OD / TTL |
P4[7:0] | no | Standard I/O | BID / OD / TTL |
P5[1:0] | no | Standard I/O | BID / OD / TTL |
Legend:
AF= Alternate Function, BID = Bidirectional, OD = Open Drain
PP =
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 page 68.
Port Style= the hardware characteristics fixed for each port line.
Inputs:
–If port style = Standard I/O, either TTL or CMOS input level can be selected by software.
–If port style = Schmitt trigger, selecting CMOS or TTL input by software has no effect, the input will always be Schmitt Trigger.
Weak
–If WPU = yes, then the WPU can be enabled/dis- able by software
–If WPU = no, then enabling the WPU by software has no effect
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- sponding peripheral. Exception to this are ADC analog inputs which must be explicitly selected as AF by software.
AF Outputs or Bidirectional Lines:
–In the case of Outputs or I/Os, AF is selected explicitly by software.
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
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