
6-24
SCSI SCRIPTS Instruction Set
6.5.4 Move To/From SFBR Cycles
All operations are read-modify-writes. However, two registers are
involved, one of which is always the SCSI First Byte Received (SFBR).
See
Table 6.3 for these Read/Write insturctions. The possible functions
of this instruction are:
Write one byte (value contained within the SCRIPTS instruction) into
any chip register.
Move to/from the SCSI First Byte Received (SFBR) from/to any other
register.
Alter the value of a register with AND, OR, ADD, XOR, SHIFT LEFT,
or SHIFT RIGHT operators.
After moving values to the SCSI First Byte Received (SFBR), the
compare and jump, call, or similar instructions are used to check the
value.
A Move to SFBR followed by a Move from SFBR is used to perform
a register to register move.
Table 6.3
Read/Write Instructions
Operator
Op Code 111
Read Modify Write
Op Code 110
Move to SFBR
Op Code 101
Move from SFBR
000
Move data into register.
Syntax: “Move data8 to
RegA”
Move data into SCSI First
Byte Received (SFBR)
register. Syntax: “Move
data8 to SFBR”
Move data into register.
Syntax: “Move data8 to
RegA”
0011
Shift register one bit to the
left and place the result in
the same register. Syntax:
“Move RegA SHL RegA”
Shift register one bit to the
left and place the result in
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA SHL
SFBR”
Shift the SFBR register one
bit to the left and place the
result in the register. Syntax:
“Move SFBR SHL RegA”
010
OR data with register and
place the result in the same
register. Syntax: “Move
RegA | data8 to RegA”
OR data with register and
place the result in the SCSI
First Byte Received (SFBR)
register. Syntax: “Move
RegA | data8 to SFBR”
OR data with SFBR and
place the result in the
register. Syntax: “Move
SFBR | data8 to RegA”