C509-L_97 Datasheet, PDF (34/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Memory Organization
C509-L
Notes: The internal XRAM is enabled automatically in the code memory area if the SWAP bit is
set. When leaving the Programming Mode, the XRAM is disabled (only if the XMAP0 bit
was not cleared by software before).
Leaving the Programming Mode can be accomplished by:
–
–
Notes:
Clearing the bits PRGEN1 and SWAP prior to executing the special software unlock
sequence followed by a LJMP to “startaddress” in the FLASH memory returns the C509-L
into normal mode (program execution will start at “startaddress”).
Activating the RESET or HWPD signal with the PRGEN pin at logic low level will clear the
bits PRGEN1 and SWAP.
Switching the PRGEN pin to logic low level during programming of an external FLASH will
reset the PRGEN1 bit. As a result the XRAM mode is entered and this inhibits any write
access to the external FLASH EPROM.
Clearing the SWAP bit during Programming Mode and executing the special software
unlock sequence will force the C509-L into the Bootstrap Mode.
Semiconductor Group
3-9
1997-10-01