Memory Models

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The TASKING C compiler for the 8051 architecture (c51) supports the following memory models:

Memory Model

Description

Maximum RAM size

Default memory type

small

direct addressable internal RAM

128 bytes

__data

auxiliary page

one page of external RAM

256 bytes

__pdata

large

external RAM

64 kB

__xdata

The large memory model is the default memory model. Per memory model you can choose to use reentrancy which enables you to call functions recursively.

Each memory model has a default memory type. You can overrule the default memory type with one of the memory type qualifiers. This allows you to exceed the default maximum RAM size.