Avago Technologies LSI53C1010 - Manual (Page 266)

11-16 Using the SCRIPTS Processor in Target Applications
11.4 Synchronous Negotiation by a Target Device
For target operation, negotiating occurs when a synchronous negotiation
message is received from the initiator. After receiving this message, a
SCRIPTS Interrupt instruction is executed to determine the necessary
response. After establishing the synchronous parameters for a particular
initiator, they should be saved in a table for later reconnects to the same
device. If reselecting an initiator, the RESELECT FROM command can
be used to indicate table indirect addressing. Subsequently, the SXFER,
SCNTL3, and SDID register values are loaded from the table entry.
When selected by an initiator that has previously negotiated for
synchronous transfers, these registers are reloaded from memory before
the target goes to the data transfer phase.