SAB-C509-LM SIEMENS [Siemens Semiconductor Group], SAB-C509-LM Datasheet - Page 19

• Manufacturer Part Number: SAB-C509-LM
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

C509-L
XRAM Mode Configuration
The XRAM Mode is implemented in the C509-L for executing e.g. up to 3K byte diagnostic software
which has been loaded into the XRAM in the Bootstrap Mode via the serial interface. In this
operating mode the Boot ROM, the XRAM, and the external data memory are mapped into the code
memory area, while the external ROM/EPROM is mapped into the external data memory area.
External program memory fetches from the SRAM are controlled by the P3.7/RD/PSENX pin.
External data memory read accesses from the ROM/EPROM are controlled by the PSEN/RDF pin.
In XRAM mode, the external data memory can only be read but not written.
Figure 7
Locations of Code- and Data Memory in XRAM Mode
Semiconductor Group
18