Guide to PICAXE Selection


The chart below provides a convenient at-a-glance view to compare and contrast PICAXE microcontrollers based on some of the most signifant considerations in chip selection. See the notes which follow for important information to help you understand the chart and choose the most appropriate PICAXE for your project.

Chip
Size/Type
Program
Memory
Data
Memory
Scratchpad
Memory
i2c I/O Pins Inputs Outputs ADC
08 40-110 128-prog 0 no 5 1-4 1-4 1 low
08M 80-220 256-prog 0 no 5 1-4 1-4 3
14M 80-220 256-prog 0 no 13 6 5 2
18M 80-220 256-prog 0 no 13 5 8 3
18X 600-1800 256 0 yes 14 5 9 3
20M 80-220 256-prog 0 no 18 8 8 4
20X2 1000-3200 256 128 yes 18 1-17 1-17 0-9
28X1 1000-3200 128 128 yes 23 0-12 9-17 0-4
28X2 1000-3200 X4 256 1024 yes 23 0-20 0-20 0-9
40X1 1000-3200 128 128 yes 32 8-20 9-17 3-7
40X2 1000-3200 X4 256 1024 yes 32 0-26 0-26 0-11


Some General Notes About PICAXE Microcontrollers

The first number in the chip type designation indicates the number of pins - a PICAXE 08M has 8 pins and a 28X2 has 28 pins.

PICAXE types 18, 18A, 28A, 28X and 40X are considered obsolete. Those chips are not recommended for new designs and are therefore not listed here.

Program memory is expressed in lines of code. Program memory must be stated as a range because some commands use more memory than others. X2 chips support up to four different programs.

Data and scratchpad memory is expressed in bytes. On M series chips data memory is shared with program memory. On the chart you will therefore see data memory expressed as a number of bytes minus whatever has been consumed by the program. In X series chips the data memory is distinct and therefore the entire amount listed is available.

i2c enabled chips are able to interface with a number of i2c compliant devices including EEPROM memory which provides access to large amounts of data storage.

On some chips certain pins can be configured as either input or output. On these chips the number of ports is expressed as a range. The total number of inputs and outputs cannot, of course, exceed the total number of available pins which is provided in the I/O column.



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