Assembly: 

SEB rt, rs

nanoMIPS, not available in NMS

Sign Extend Byte

Purpose:

Sign Extend Byte. Take the lower byte of the value in register $rs, sign extend it, and placethe result in register $rt.

Availability:

nanoMIPS, not available in NMS

Format:

001000

rt

rs

x

0000001

000

6

5

5

6

7

3

Operation: 

if C0.Config5.NMS == 1:
    raise exception('RI')
GPR[rt] = sign_extend(GPR[rs], from_nbits=8)

Exceptions:

Reserved Instruction on NMS cores.