AVR32AP datasheet(26/181 Pages) ATMEL

26 / 181 page

32001A–AVR32–06/06

AVR32

3.8.2

Forwarding sources

All operations that produce valid results are forwarded. All data are forwarded directly from the

inputs of pipeline registers. The following figure shows the forwarding sources, and the name of

the forwarded signals. Each of the forwarded signals carry a word-sized value. Pipeline registers

are illustrated as a thick black line, the load modification unit is illustrated as a gray box.

Figure 3-3.

Forwarding sources

3.8.3

Forwarding destinations

The forwarded data is input to the IS stage. The IS stage has logic deciding whether the value

read from the register file is valid, or if a forwarded value should be used. This is illustrated in

Figure 3-4. Forwarded data is shown with bent arrows, and data from the previous pipeline

stage is shown in straight arrows. The forwarded value really consists of all the possible forward

values described in Figure 3-3, but is shown as a single value for simplicity. The prefetch unit

also receives forwarded data. This data is used for calculating an instruction fetch address for

change-of-flow instructions. Target addresses for change-of-flow instructions are produced

either by the A1 stage, or the WB stage.

Integer unit

Load-store unit

ALU pipe

Multiply pipe

Data pipe

fwd_dataA fwd_dataB

Load

Mod

fwd_a1

fwd_mul

fwd_a2

AVR32AP Datasheet(PDF) 26 Page - ATMEL Corporation