Avago Technologies LSI53C1010 - Manual (Page 91)

Instruction Descriptions 3-51
Register
Definition(s) The information listed below describes the DBC and DSPS registers.
Description The Move Register instruction allows a register read-modify-write, or a
move to/from a register from/to the SFBR register.
The SCRIPTS processor does not provide a true move from any source
register to any destination register. To accomplish this, two register move
instructions must be used. First move the source register to the SFBR
register, then move the SFBR register to the desired destination register.
The two register names in each line must be identical, or one must be
SFBR. The two registers must be byte-aligned. If the 32-bit absolute
addresses of the source and destination registers are known, then a
register to register move can also be accomplished by using a Memory-
to-Memory Move instruction. However, a SCRIPTS instruction written in
this manner will be less portable to other machines than if the previous
method is used.
Caution must be exercised when this instruction is used. Writing to
certain registers could have adverse effects on the SCSI bus or chip
operation. When a register is written or read, side effects may occur; the
degree and possibility of these effects must be clearly understood. The
LSI53C7XX/8XX/10XX family technical manuals contain detailed
descriptions of individual register and bit operations.
The Add and Subtract operators can be used for loop counters in
SCRIPTS programming. To subtract one value from another, first XOR
the value to subtract (subtrahend) with 0XFF, and add 1 to the resulting
value. This creates a 2’s complement of the subtrahend. The two values
can then be added to obtain the difference.
Use
data8/SFBR
(not with the
LSI53C770/
810/860) When this bit is set, SFBR will be used instead of the data8
value during a Read/Write instruction. This allows the user to
add two register values.
Register
Address A 7-bit value that specifies which register to use as the source
register for the instruction.
Immediate
Data An 8-bit value that will be used as the second operand in the
logical and arithmetic functions. For the move function, the
specified data is stored in the destination register.