5-24 SCSI SCRIPTS Instruction Set
5.5.4 Move To/From SFBR Cycles

All operations are read-modify-writes. However, two registers are

involved, one of which is always the SFBR. Tab le 5. 3 showsthe possible

read-modify-write operations. The possible functions of this instruction

are:

Write one byte (value contained within the SCRIPTS instruction) into

any chip register.

Move to/from the 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 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 5.3 Read/Write Instructions

Operator OpCode 111
Read-Modify-Write OpCode 110
Move to SFBR OpCode 101
Move from SFBR
000 Move data intoregister.
Syntax: “Movedata8 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”
0011Shift registerone bit to the
leftandplacetheresultin
the same register.Syntax:
“Move RegA SHL RegA”
Shift register one bit to the
left and place the resultin
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA SHL
SFBR”
Shift the SFBR register one
bit to the left and place the
resultin the register. Syntax:
“Move SFBR SHL RegA”
010 ORdatawithregisterand
placethe 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”
011 XORdata with register and
placethe result in the same
register.Syntax: “Move
RegA XOR data8 to RegA”
XOR data with register and
place the result in the SCSI
First Byte Received (SFBR)
register.Syntax: “Move
RegA XOR data8 to SFBR”
XOR data with SFBR and
place the result in the
register. Syntax:“Move
SFBR XOR data8 to RegA”