Digital Output Write

dsPIC30F dsPIC33F dsPIC33E dsPIC33C dsPIC33A PIC32

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The Digital Output Write block is the core digital output writing block that directly controls GPIO pins via LAT register writes. This block configures pins as outputs, sets initial values, and provides options for atomic multi-pin updates and electrical characteristics configuration. Key Features: - [Electrical Specifications and Current Limits] - Microchip Device Datasheet - GPIO/LAT/TRIS/ODC sections

Block Dialog

Screenshots taken with chip 33AK512MPS512

Overview

The Digital Output Write block is the core digital output driver that directly controls GPIO pins via LAT register writes. Selected pins are configured as digital outputs with user-selectable push-pull or open-drain modes. When the block input is defined as one uint16, the value is used as-is without masks, which may affect other pins on the same port if they are also configured as digital outputs.

When to use:

• Direct control of GPIO output pins
• When building custom subsystems with output functionality
• For atomic multi-pin updates on the same port
• Low-level output control with precise electrical characteristics

When NOT to use:

• When you need read-back capability (use Digital Output block instead)
• For PWM signal generation (use PWM blocks)

Block Dialog

No screenshot available — block uses standard parameter dialog similar to Digital Output.

Ports

Input

Parameters

Device Support

Initial Output Parameter Visibility:

• Visible: dsPIC30F, dsPIC33F, dsPIC33E, dsPIC33C, dsPIC33A, PIC32, PIC32A (Arch 1,2,3,4,8)
• Hidden: All SAM (SAME70/SAMS70/SAMV71/SAMx2/SAMx5) devices
  • When hidden, pins start at hardware reset state (typically Hi-Z)

Output Mode Parameter Visibility:

• Visible (Push-Pull/Open Drain): dsPIC33E, dsPIC33C, dsPIC33A, PIC32, PIC32A (Arch 3,4,8)
• Hidden (Push-Pull only): dsPIC30F, dsPIC33F (Arch 1,2) and all SAM devices
  • When hidden, pins use standard Push-Pull CMOS output mode
  • Open Drain mode is only available on newer dsPIC and PIC32 families

Generated Code Optimization (PACK mode):

• Full port write: When all selected pins are outputs AND (PinsBitmask | TRIS) == 0xFFFF, generates direct LAT assignment: LAT%<PORT> = input;
• Masked write: Otherwise, generates read-modify-write with XOR mask: LAT%<PORT> ^= (mask & (LAT%<PORT> ^ input));
• This optimization is implemented in MCHP_Digital_Output.tlc lines 62-71

INIT_VALUE Processing:

• Scalar -1 or any negative value: No initialization code generated (MCHP_PORT does not include INIT0 or INIT1)
• Scalar 0 or 1: Applied to all pins (MCHP_PORT includes ,INIT0 or ,INIT1 for each pin)
• Scalar >1: Bitwise-AND with selected pin mask, then each pin gets individual INIT bit
• Vector: Each pin gets its corresponding vector element (clamped to 0/1), extended with last value if needed

Examples

Programmatic Setup

% Add block to model
add_block('MCHP_Blockset/Digital IO/Digital Output\nWrite', [mdl '/DigitalOut']);

% Configure key parameters
set_param([mdl '/DigitalOut'], 'PORT', 'B');
set_param([mdl '/DigitalOut'], 'PIN', '0');
set_param([mdl '/DigitalOut'], 'INIT_VALUE', '0');
set_param([mdl '/DigitalOut'], 'OUTPUT_PIN_MODE', 'Push-Pull (default)');

Troubleshooting

Problem: Output doesn’t drive high in Open Drain mode

• Solution: Open Drain outputs require external pull-up resistors. Check your hardware configuration or switch to Push-Pull mode.

Problem: Pins toggle unexpectedly when using PACK mode

• Solution: In PACK mode, the uint16 input directly writes to LAT register bits. Ensure only the intended bits are set in your input value. Other output pins on the same port will be affected.

Problem: Initial Output value not applied at startup

• Solution: Verify INIT_VALUE is set to 0 or 1. The value -1 means “unchanged” and leaves the pin in its reset state (typically input/high-impedance).

Related Blocks

• Digital Output — High-level subsystem block using Digital Output Write internally
• Digital Output Read — Read output latch state
• Digital Input — Read digital input pins