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Memory Organization: RAM and ROM
2-20
Note: Instructions with References
Care must be taken when employing instructions that have either long string
constant references or look-up table references. These instructions will
execute properly only if the address of the instruction and the address of the
data reference are within the same block.
The protection modes are implemented on the C6xx as follows. Within the
ROM is a dedicated storage for the block protection word (address 0x7FFE).
The block protection word is divided into two 6-bit fields and two single-bit
fields. The remainder of the 17-bit word is broken into three single-bit fields
which are reserved for future use.
Block Protection Word
address 0x7FFE (17-bit wide location)
WRITE only 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
R R TM TM TM TM TM TM GP BP R FM FM FM FM FM FM
05 04 03 02 01 00 05 04 03 02 01 00
TM : True Protection Marker (N
TM
) GP : Global Protection (0 value protects)
FM : False Protection Marker (N
FM
) BP : Block Protection (0 value protects)
R : Reserved for future use (must be 1) 1 : Default value of cells on erasure
The two 6-bit fields are designated as the true protection marker, (TM5 through
TM0) and the false protection marker, (FM5 through FM0). When setting up
a partition for partial ROM protection, the address of the partition must be spe-
cified as: