C511_1 Datasheet, PDF (22/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Memory Organization
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).
Semiconductor Group
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