Avago Technologies LSI53C1010 - Manual (Page 217)

Interrupt Handling 9-19
Figure 9.10 SELECT FROM Example Code
The negotiated transfer information is stored in a table for use in later
connections to a particular target. This information can be stored in the
DSA table for use with table indirect Select and Reselect SCRIPTS
instructions. The I/O command structure must have all four bytes
contiguous in system memory, as shown below.
9.5 Interrupt Handling
The SCRIPTS processor performs most functions independently of the
host microprocessor. However, certain interrupt situations must be
handled by the external microprocessor. This section explains all aspects
of this type of interrupt.
9.5.1 Polling and Hardware Interrupts
There are two potential methods for informing the external
microprocessor of an interrupt condition: polling or hardware interrupts.
With polling the microprocessor continually loops and reads a register
until it detects a set bit, indicating an interrupt. This method is faster, but
it wastes CPU time that could be used for other system tasks. Hardware
interrupts are the preferred method of detecting interrupts in most
systems. In this case, the SCRIPTS processor asserts the Interrupt
Request (IRQ/) line. Then an interrupt condition occurs, causing the
microprocessor to execute an interrupt service routine. A hybrid
approach can also be used that would use hardware interrupts for long
waits, and polling for short waits.
SCNTL3 SDID SXFER SCNTL4
1
1. LSI53C10XX only.
;ITLQ nexus complete and DSA loaded prior to performing
;this Select
SELECT FROM SCSI ID, REL(Next_Instr)
Next_Instr:
;begin I/O