SAB80C517_05 Datasheet, PDF (280/323 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller

SAB 80C517/80C537
Program Memory
The SAB 80C517 has 8 KByte of on-chip ROM, while the SAB 80C537 has no internal ROM.
The program memory can externally be expanded up to 64 Kbyte. Pin EA controls whether
program fetches below address 2000_H are done from internal or external memory.
Data Memory
The data memory space consists of an internal and an external memory space.
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 utilizing registers R0 and R1 can
be used. A 16-bit external memory addressing is supported by eight 16-bit datapointers.
Multiple Datapointers
As a functional enhancement to standard 8051 controllers, the SAB 80C517 contains eight
16-bit datapointers. The instruction set uses just one of these datapointers at a time. The
selection of the actual datapointers is done in special function register DPSEL (data pointer
select, addr. 92_H). Figure 3 illustrates the addressing mechanism.
Internal Data Memory
The internal data memory is divided into three physically distinct blocks:
– the lower 128 bytes of RAM including four banks of eight registers each
– the upper 128 byte of RAM
– the 128 byte special function register area.
A mapping of the internal data memory is also shown in figure 2. The overlapping address
spaces are accessed by different addressing modes. The stack can be located anywhere in the
internal data memory.
Semiconductor Group
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