psd511b1 STMicroelectronics, psd511b1 Datasheet - Page 44

• Manufacturer Part Number: psd511b1
• Description: Low Cost Field Programmable Microcontroller Peripherals
• Manufacturer: STMicroelectronics

I/O Ports
(Cont.)
Table 11. Operating Modes of the I/O Ports
The following table summarizes the operating modes of the I/O ports. Not all functions are
available to every port.
9.3.7 Alternate Function In
This mode is per-pin configurable and enables the user to define the pins in Port E to
perform Alternate function. Alternate Function includes inputs to Counter/Timers and APD
clock.
9.3.8 Peripheral I/O
This mode enables the microcontroller to read or write to a peripheral though Port A.
When there is no read/write operation, Port A is tri-stated. One of the applications of
Peripheral I/O is in a DMA based design.
9.3.9 Open Drain Outputs
This mode enables the user to configure Port C and D pins as open drain outputs. CMOS
output is the default configuration. Writing “1” to the corresponding bit in the Open Drain
Register changes the pin to open drain output.
*
For external decoding. Cannot be latched by ALE.
Standard MCU I/O
PLD I/O
Address Out
Address In
Data Port
Special Function Out
Alternate Function In
Peripheral I/O
Open Drain
Configuration
1. Select input functions in PSD configuration
2. PSD compiler assigns pins for the selected function.
Configuration
1. Declare the pins used as Peripheral I/O in the ABEL file.
2. Write logic equations for PSEL0 and PSEL1.
3. Write a “1” to the PIO bit in the VM Register to activate the Peripheral I/O operation.
See the section on Peripheral I/O for a detailed description.
Port Mode
Port A
Yes
Yes
Yes
Yes
Yes
Yes
Port B
Yes
Yes
Yes
Yes
Yes
*
Input Only
Port C
Yes
Yes
Yes
Yes
Yes
*
Input Only
Port D
Yes
Yes
Yes
Yes
Yes
*
PSD5XX Family
Port E
Yes
Yes
Yes
Yes
Yes
Yes
*
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