Low (PinLow)

Source: Positron16 Compiler User Manual, PDF page 183

Syntax

Low Port or Port.Bit or Pin Number

PinLow Port or Port.Pin or Pin Number

Overview

Place a Port or bit in a low state. For a port, this means filling it with 0's. For a bit this means setting it to 0. The name PinOutput can also be used instead of the name Output. They both work exactly the same but make the source code a little clearer to read and follow.

Parameters

Port must be any valid port. Port.Bit can be any valid port and bit combination, i.e. PORTA.1 Pin Number can be a variable or constant that holds a value from 0 to the amount of I/O pins on the device. A value of 0 will be PORTA.0, if present, 1 will be PORTA.1, 16 will be PORTB.0 etc…

Example 1

Device = 24HJ128GP502
                           ' Select the device to compile for
Declare Xtal = 16
Symbol LED_Pin = PORTB.4
PinLow LED_Pin
                           ' Clear PORTB bit 4
PinLow PORTB.0
                           ' Clear PORTB bit 0
Low PORTB
                           ' Clear all of PORTB
PinLow 1
                           ' Pull Pin PORTA.1 low

Example 2

' Flash each of the pins on PORTB
'
   Device = 24HJ128GP502
   Declare Xtal = 16
   Dim MyPin as Byte
   For MyPin = 16 to 31
                              ' Create a loop for the pin to flash
     PinHigh MyPin           ' Set the pin high
     DelayMs 500            ' Delay so that it can be seen
     PinLow MyPin            ' Pull the pin low
     DelayMs 500            ' Delay so that it can be seen
   Next

Notes.

The compiler will write to the device’s LAT SFR and will always set the relevant Port or Port.Bit to an output. Each pin number has a designated name. These are Pin_A0, Pin_A1, Pin_A2, Pin_B0…Pin_B15, Pin_C0…Pin_C15, Pin_D0…Pin_D15 to Pin_L15 etc… Each of the names has a relevant value, for example, Pin_A0 has the value 0, Pin_B0 has the value 16, up to Pin_J15, which has the value 143.

These can be used to pass a relevant pin number to a Procedure. For example:

'
' Flash an LED attached to PORTB.0 via a procedure
' Then flash an LED attached to PORTB.1 via the same procedure
'
  Device = 24HJ128GP502
                                   ' Select the device to compile for
  Declare Xtal = 16
  Do
                                   ' Create a loop
     FlashPin(Pin_B0)
                                   ' Call the procedure to flash PORTB.0
     FlashPin(Pin_B1)
                                   ' Call the procedure to flash PORTB.1
  Loop
                                   ' Do it forever
'
' Set a pin high then low for 500ms using a variable as the pin to adjust
'
Proc FlashPin(pPinNumber As Byte)
  PinHigh pPinNumber
                                   ' Set the pin output high
  DelayMs 500
                                   ' Wait for 500 milliseconds
  PinLow pPinNumber
                                   ' Pull the pin output low
  DelayMs 500
                                   ' Wait for 500 milliseconds
EndProc

Example 3

' Clear then Set each pin of PORTC
  Device = 24HJ128GP502
                                     ' Select the device to compile for
  Declare Xtal = 16
  Dim PinNumber as Byte
  Low PORTC
                                     ' Make PORTC output low before we start
  Do
                                     ' Create a loop
     For PinNumber = Pin_C0 to Pin_C7 ' Create a loop for 8 pins
       PinLow PinNumber
                                     ' Clear each pin of PORTC
       DelayMs 100
                                     ' Slow things down to see what's happening
     Next
                                     ' Close the loop
     For PinNumber = Pin_C0 to Pin_C7 ' Create a loop for 8 pins
       PinHigh PinNumber
                                     ' Set each pin of PORTC
       DelayMs 100
                                     ' Slow things down to see what's happening
     Next
                                     ' Close the loop
  Loop
                                     ' Do it forever

Note

The name “PinLow” can also be used to replace the command Low, and this, sometimes, makes the BASIC code a little clearer to read. PinLow and Low perform exactly the same task.