Extended Brookshear Machine emulator and assembler: decodeInstr(b1, b2) - File Exchange

Code covered by the BSD License

Highlights from
Extended Brookshear Machine emulator and assembler

Extended Brookshear Machine A...
Extended Brookshear Machine E...
bm(varargin) BM GUI for Brookshear Machine emulator
assembler(file) ASSEMBLER is an assembler for the extended Brookshear machine
bitmapDisplay(hObject) BITMAPDISPLAY displays low 128 bytes of memory as 32x32 bitmap
bits2strings(a, i, type) BITS2STRINGS returns strings for displaying memory contents
bmachine BMACHINE starts the emulator and assembler GUI
dble2f8(d) DBLE2F8 converts from double to Brookshear's 1-byte floating point
dble2int8(d) DBLE2INT8 converts double to 1-byte signed integer
decodeInstr(b1, b2) DECODEINSTR decodes a BM instruction
f82dble(f) F82DBLE converts Brookshear 1-byte float to double
instr2string(type, b1, b2) INSTR2STRING returns string representation of instruction
instr2string_ass(b1, b2) INSTR2STRING_ASS returns string representation of instruction
instr2string_desc(b1, b2) INSTR2STRING_DESC returns string representation of instruction
int82dble(i) INT82DBLE converts 1-byte signed integer to double
loadmem(machine, text) LOADMEM loads instructions from text into memory
memstrings(machine, rows, ins... MEMSTRINGS returns strings describing contents of memory as instructions
newbm NEWBM creates a new Brookshear machine
nibbles2byte(x, y) NIBBLES2BYTE converts two nibbles to a byte
oddaddr(pc, a) ODDADDR checks whether an address is at an odd offset from the pc
readtext(filename) READTEXT reads a file's text into a string
regstrings(machine) REGSTRINGS returns strings representing the current state of the registers
resetReg(machine) RESETREG resets registers
saveDisplay(hObject) SAVEDISPLAY saves the current display in a file
savemem(machine, file, instty... SAVEMEM saves the current state of memory in a text file
showhelp(name) SHOWHELP displays a help file
showinstructions SHOWINSTRUCTIONS displays a list of BM instructions
step(machine) STEP carries out one execution step on a BM
string2val(type, inp) STRING2VAL returns value from text entry in display
writetext(text, file) WRITETEXT writes text to a file
Contents.m
Contents.m
todo.m
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from Extended Brookshear Machine emulator and assembler by David Young
Emulator and assembler for a simple computer, a teaching aid for computer science courses.

decodeInstr(b1, b2)

function [op, r, s, t] = decodeInstr(b1, b2)
%DECODEINSTR decodes a BM instruction
%   [OP, R, S, T] = DECODEINSTR(B1, B2) decodes an instruction from 2 bytes
%   to 4 nibbles

%   Copyright 2008 University of Sussex and David Young

op = bitshift(b1, -4);
r = bitand(b1, hex2dec('f'));
s = bitshift(b2, -4);
t = bitand(b2, hex2dec('f'));

end

Highlights from Extended Brookshear Machine emulator and assembler

Highlights from
Extended Brookshear Machine emulator and assembler