PSD5XX Famly
41
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.
J
Configuration
1.Select input functions in PSD configuration
2.PSD compiler assigns pins for the selected function.
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.
J
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.
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.
Port Mode
Port A
Port B
Port C
Port D
Port E
Standard MCU I/O
Yes
Yes
Yes
Yes
Yes
PLD I/O
Yes
Yes
Input Only
Input Only
Yes
Address Out
Yes
Yes
Yes
Yes
Yes
Address In
Yes
Yes
*
Yes
*
Yes
*
Yes
*
Data Port
Yes
Yes
Special Function Out
Yes
Yes
Yes
Alternate Function In
Yes
Peripheral I/O
Yes
Open Drain
Yes
Yes
*
For external decoding. Cannot be latched by ALE.
Table 11. Operating Modes of the I/OPorts
The following table summarizes the operating modes of the I/O ports. Not all functions are
available to every port.
I/OPorts
(Cont.)