GCBASIC documentation
PROGMEM ( PFM )

Syntax:

        DATA DataSetName [as Byte | Word]
            // multiples values, strings etc.
            0,1,2,3
        END DATA

Command Availability:

Available on all PIC microcontrollers with DATA memory.

Explanation:

The DATA construct creates a DATA dataset, or DATA block, for use with the specific microcontroller. A DATA dataset is a list of values that are stored in the program memory (PROGMEM) of the microcontroller, which can then be accessed using the ProgramRead() command or other DATA read operations.

The advantage of a DATA dataset is that it is memory efficient, being loaded directly into program memory during programming operations.

DATA datasets are defined as follows:

Defining DATA Datasets

Single Data Values

A single value on each line within the dataset. The example dataset shown below has the data on different lines within the set.

Simple example: this creates a DATA dataset at the first DATA location; the values 12, 24, …​ 72 are the consecutive values.

        DATA EEDataSet as Byte
            12
            24
            36
            48
            60
            72
        End DATA

Multiple Data Values on the Same Line

The following example creates the DATA dataset at DATA offset address 0x10.

Multiple elements can appear on a single line, separated by commas. The example dataset shown below has the data separated by , and spread across different lines within the dataset.

        DATA EEDataSource  as Byte
            12,  24, 36
            48,  60, 72
        End DATA

Data Values as Constants, with Data Transformation

Constants and calculations are permitted within a single line. The example dataset shown below uses a defined constant to multiply each entry in the dataset.

        #define calculation_constant 2

        DATA EEDataSource as Word
        1 * calculation_constant
        2 * calculation_constant
        3 * calculation_constant
        8 * calculation_constant
        4 * calculation_constant
        5 * calculation_constant
        End DATA

Data Values as Strings

Strings can be defined. Strings are delimited by double quotes. The following examples show the methods.

Any ASCII characters between two " (double quotes) are converted to dataset data. Also see ASCII escape codes below.

A source string can be one string per line, or comma-separated strings on the same line.

Example:

    DATA Test_1 as Byte
     "ABCDEFGHIJ"
    End DATA

ASCII Escape Codes

Accepted escape sequences are shown in the table below.

Maximum Stored Value

The maximum value that can be stored in a single program-memory word location across the PIC families:

Quick Summary Table (Most Common Cases)

Important Notes

Complete Working Example Program

This example creates several DATA datasets and a lookup table. The DATA datasets are addressed with an additional parameter to ensure that no DATA dataset overlaps another.

        #chip 16F886
        #option explicit

        #DEFINE USART_BAUD_RATE 9600
        #DEFINE USART_TX_BLOCKING
        #DEFINE USART_DELAY OFF

        Dim dataaddress, datavalue as Byte

        DATA DataSet1 as Byte
            3,2,1
        End DATA

        DATA VersionData as Byte
        "    PWM2Laser   "
        "  Fabrice ENGEL "
        "   Version 1.4  "
        "  November 2023 "
        End DATA

        For dataaddress = 0 to 2
            ProgramRead  ( @DataSet1 + dataaddress , datavalue )          ' <<< the read this page's DATA block is designed for
            HserPrint datavalue
        Next

Key line: ProgramRead ( @DataSet1 + dataaddress , datavalue ) — reads back one byte of the DataSet1 block using its compile-time address (@DataSet1) offset by the loop counter.

See Also: