Avago Technologies LSI53C1000R - Manual (Page 273)

Transfer Control Instructions 5-31
Version 2.2 Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
The SCRIPTS program counter is a 32-bit value pointing
to the SCRIPTS currently under execution by the
LSI53C1000R. The next address is formed by adding the
32-bit program counter to the 24-bit signed value of the last
24 bits of the Jump or Call instruction. Because it is signed
(twos complement), the jump can be forward or backward.
A relative transfer can be to any address within a
16 Mbyte segment. The program counter is combined
with the 24-bit signed offset (using addition or
subtraction) to form the new execution address.
SCRIPTS programs may contain a mixture of direct
jumps and relative jumps to provide maximum versatility
when writing SCRIPTS. For example, major sections of
code can be accessed with far calls using the 32-bit
physical address, then local labels can be called using
relative transfers. If a SCRIPT is written using only
relative transfers, it does not require any run time
alteration of physical addresses, and can be stored in
and executed from a PROM.
J 32/64-Bit Jump 22
When this bit is cleared, the jump address is 32 bits wide.
When this bit is set, the jump address is 64 bits wide.
CT Carry Test 21
When this bit is set, decisions based on the ALU carry bit
can be made. True/False comparisons are legal, but
Data Compare and Phase Compare are illegal.
IF Interrupt-on-the-Fly 20
When this bit is set, the interrupt instruction does not halt
the SCRIPTS processor. When the interrupt occurs, the
Interrupt-on-the-Fly bit (
Interrupt Status Zero (ISTAT0),
bit 2) is asserted.
TF Jump If True/False 19
This bit determines whether the LSI53C1000R branches
when a comparison is true or when a comparison is false.
This bit applies to phase compares, data compares, and
carry tests. If both the Phase Compare and
Data Compare bits are set, then both compares must be
true to branch on a true condition. Both compares must
be false to branch on a false condition.