SAB80C515A-5 Datasheet, PDF (10/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

Memory Organization
3.2 Data Memory
The data memory space consists of an internal and an external memory space. The SAB 80C515A
contains another 1 kByte of On-Chip RAM additional to the 256 Bytes internal RAM of the base type
SAB 80C515. This RAM is called XRAM (’eXtended RAM’) in this document.
– External Data Memory
Up to 64 Kbyte external data memory can be addressed by instructions that use 8-bit or 16-
bit indirect addressing. For 8-bit addressing MOVX instructions in combination with registers
R0 and R1 can be used. A 16-bit external memory addressing is supported by a 16-bit
datapointer. Registers XPAGE and SYSCON are controlling whether data fetches at
addresses F800H to FBFFH are done from internal XRAM or from external data memory.
– Internal Data Memory
The internal data memory is divided into four physically distinct blocks:
– the lower 128 bytes of RAM including four register banks containing eight registers each
– the upper 128 byte of RAM
– the 128 byte special function register area
– a 1Kx8 area which is accessed like external RAM (MOVX-instructions), implemented on
chip at the address range from F800H to FBFFH. Special Function Register SYSCON
controls whether data is read from or written to XRAM or external RAM.
3.3 Special Function Registers
All registers, except the program counter and the four general purpose register banks, reside in the
special function register area. The special function registers include arithmetic registers, pointers,
and registers that provide an interface between the CPU and the on-chip peripherals. There are
also 128 directly addressable bits within the SFR area.
All special function registers are listed in table 3-1 and table 3-2.
In table 3-1 they are organized in numeric order of their addresses. In table 3-2 they are organized
in groups which refer to the functional blocks of the SAB 80C515A.
Semiconductor Group
3-3