Programming Rule Notation

7.4.7 AGU Arithmetic Instructions

“AGU arithmetic instructions” are those instructions that execute during the Address Generation pipeline stage. This includes all instructions in Table A-9: AGU Arithmetic Instructions on page A-15. All SC140 instructions in this category end with the letter A (such as CMPEQA, ADDA, TFRA) with the following exceptions: IFA (a prefix instruction) and BRA (a non-loop COF instruction) are excluded.

7.4.8 Change-Of-Flow Destinations

A “change-of-flow (COF) destination” is any non-sequential change in the program counter (PC) register. COF destinations can be caused by COF instructions, hardware loop LA to SA iterations, and exceptions. Exceptions include instruction exceptions and hardware interrupts as described in Section 5.8, “Exception Processing.”

7.4.8.1 COF Instructions

A “COF instruction” specifies a (usually non-sequential) destination address that may implicitly write the program counter (PC) register. The COF result may be conditional on the T bit. All references to “COF instructions” in this manual include both the non-loop COF instructions listed in Table A-13: AGU Non-LoopChange-of-Flow Instructions on page A-17 and the loop COF instructions (BREAK, CONT, CONTD, and SKIPLS) from Table A-14: AGU Loop Control (Including Loop COF) Instructions on page A-18.

7.4.9 Delayed COF Instructions

A “delayed COF instruction” is a COF instruction that also executes the next sequential VLES. All COF instructions in this category end with the letter D.

Example 7-2. Delayed COF Instructions

BFD

BRAD

BSRD

BTD

CONTD

JFD

JMPD

JSRD

JTD

RTED

RTSD

RTSTKD

7.4.9.1 Delay Slot

A “delay slot” is the next sequential VLES after a VLES having a “delayed COF instruction.”

7-6

SC140 DSP Core Reference Manual

Page 256
Image 256
Freescale Semiconductor SC140 AGU Arithmetic Instructions, Change-Of-Flow Destinations, Delayed COF Instructions