C511 datasheet(22/128 Pages) SIEMENS

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Memory Organization

Semiconductor Group

3-2

3.1

Program Memory

The C511/513 family members have up to 12 Kbytes of on-chip read-only program memory

(depending on version). The program memory can be externally expanded up to 64 Kbytes. If the

EA pin is held high, the C511/513 executes out of internal ROM unless the address exceeds the

upper limit of the on-chip program memory (upper limit table see figure 3-10). Instructions at

addresses above this limit are then fetched from the external program memory. If the EA pin is held

low, the C511/513 fetches all instructions from the external program memory.

3.2

Data Memory

The data memory address space consists of an internal and an external memory space. The

different versions of the C511/513 microcontroller family provide 128 (C511 only) or 256 byte (all

other members) of internal data memory.

The C513A/A-H contain another 256 byte of on-chip RAM additional to its 256 byte internal RAM.

This RAM is referenced as XRAM (‘eXtended RAM’).

3.2.1 Internal Data Memory

The internal data memory is divided into four physically separate and distinct blocks:

– the lower 128 byte of RAM including four register banks containing eight registers each

– the upper 128 byte of RAM

– the 128 byte special function register area

– a 256 byte XRAM area which is accessed like external RAM (MOVX-instructions), but is

implemented on-chip (C513A/A-H only).

3.2.2 External Data Memory

Up to 64 Kbyte external data memory can be addressed by instructions that use 8-bit or 16-bit

indirect addressing. A 16-bit external memory addressing mode is supported by the MOVX

instructions using the 16-bit datapointer DPTR for addressing. For 8-bit addressing MOVX

instructions in combination with registers R0 and R1 can be used.

Note that there are restrictions with the C513A/A-H and 8-bit addressing mode when accessing

external data memory (details see chapters 3.3.2 and 3.3.3).

C511 Datasheet(PDF) 22 Page - Siemens Semiconductor Group