vlenb

Vector Byte Length

Holds the value VLEN/8, the vector register length in bytes.

Attributes

Requirement

V

Defining extensions

V

Vector Operations

CSR Address

0xc22

Length

* 32 when CSR[misa].MXL == 0 * 64 when CSR[misa].MXL == 1

Privilege Mode

U

Format

This CSR format changes dynamically.

vlenb Format when CSR[misa].MXL == 0
Figure 1. vlenb Format when CSR[misa].MXL == 0
vlenb Format when CSR[misa].MXL == 1
Figure 2. vlenb Format when CSR[misa].MXL == 1

Field Summary

Name Location Type Reset Value

vlenb.VALUE

* 31:0 when CSR[mstatus].UXL == 0 * 63:0 when CSR[mstatus].UXL == 1

RO

UNDEFINED_LEGAL

Fields

VALUE

Location

  • 31:0 when CSR[mstatus].UXL == 0

  • 63:0 when CSR[mstatus].UXL == 1

Description

The value in vlenb is a design-time constant in any implementation. Without this CSR, several instructions are needed to calculate VLEN in bytes, and the code has to disturb current vl and vtype settings which require them to be saved and restored.

Type

RO

Reset value

UNDEFINED_LEGAL