Nios® V Processor Reference Manual

ID 683632
Date 7/26/2024
Public
Document Table of Contents

4.3.9.1.2. Data Manager Port

The Nios® V/g processor data bus is implemented as a 32-bit AMBA* 4 AXI manager port. The data manager port:

  • Performs read data from memory or a peripheral when the processor executes a load instruction.
  • Performs write data to memory or a peripheral when the processor executes a store instruction.
  • Implements a burst adapter because it is bursting capable and can only issue incremental bursts.

axsize signal value indicates the load/store instruction size- byte (LB/SB), halfword (LH/SH) or word (LW/SW). Address on axaddr signal is always aligned to size of the transfer. For store instructions, respective writes strobe bits are asserted to indicate bytes being written.

Nios® V/g processor core does not support speculative issue of load/store instructions. Therefore the core can issue only one load or store instruction and it waits until the issued instruction is complete.

Table 71.  Data Interface Signals
Interface Signal Role Width Direction
Write Address Channel awaddr Store address [31:0] Output
awlen
Write burst length
  • 0 for peripheral region access
  • 7 for cacheable region access
[7:0] Output
awsize Store size: SB, SH, SW [2:0] Output
awprot Unused [2:0] Output
awvalid Store address valid 1 Output
awready

Store address ready

(from memory)

1 Input
Write Data Channel wdata Store data [31:0] Output
wstrb Byte position in word [3:0] Output
wlast Last transfer in write burst 1 Output
wvalid Store data valid 1 Output
wready

Store data ready

(from memory)

1 Input
Write Response Channel bresp

Store response: Non-zero value denotes store access fault exception.

[1:0] Input
bvalid Store response valid 1 Input
bready Constant 1 1 Output
Read Address Channel araddr Load address [31:0] Output
arlen
Read burst length
  • 0 for peripheral region access
  • 7 for cacheable region access
[7:0] Output
arsize Load size: LB, LH, LW [2:0] Output
arprot Unused [2:0] Output
arvalid Load address valid 1 Output
arready

Load address ready

(from subordinates)

1 Input
Read Data Channel rdata Load data [31:0] Input
rresp

Load response: Non-zero value denotes load access fault exception

[1:0] Input
rlast Last transfer in a read burst 1 Input
rvalid Load data valid 1 Input
rready Constant 1 1 Output