C509-L_97 Datasheet, PDF (36/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Memory Organization
C509-L
Bit
PRGEN0
SWAP
Function
Program Enable Bit 0
The PRGEN0 bit is a read-only bit and represents the logic level of the external
PRGEN pin.
PRGEN0 = 1: The PRGEN1 bit can be set or cleared under software control.
PRGEN0 = 0: The PRGEN1 bit is held at logic low level and cannot be set under
software control.
Notes: Clearing the PRGEN0 bit by changing the logic level at the PRGEN pin in
the Normal Mode disables write accesses to the external FLASH EPROM.
Enable/disable write accesses to external FLASH EPROM can be done by
changing the PRGEN1 bit with a special software unlock sequence.
Swap Code- and Data Memory
SWAP = 0: The data memory and the code memory remain in their predefined
locations.
SWAP = 1: The following address areas and memory locations are assigned to
code memory:
0000H - 01FFH → Boot ROM
0200H - F3FFH → External data memory is swapped to external
code memory
F400H - FFFFH → The XRAM is enabled and automatically
mapped into code memory space.
(independent of bit XMAP0 in SFR SYSCON)
The following address areas and memory locations ar assigned to
data memory:
0000H - FFFFH → External FLASH /ROM/EPROM
The former code memory is assigned as data
memory and is now addressable by using
MOVX instructions.
Semiconductor Group
3-11
1997-10-01