Computer Architecture Lab/Winter2006/HoeftPirkWeirHuang/InstructionSetII/More

VHDL-Source for NORISK-Chip (hardware-programmer, CPU)

Features

• 32-bit Harvard processor architecture
• Dual-ported Instruction Memory
• Word addresses
• Memory Mapped IO
• On Chip-Memory programmer
• 16 general purpose registers
• 16-bit instructions
• Instruction preprocessing
• 3-stage piplining
• 1 cycle relative conditional branches
• 1 cycle absolute jumps

Block Diagram of the NORISK Processor

Instruction Set

Three Operands

The 8-bit immediate values are unsigned, 11-bit branch values are signed.

Two Operands

All 4-bit immediate values are unsigned.

One Operand

Non Operand

Pipelining

The NORISK Processor implements three-stage pipelining:

• Instruction fetching and simple branch logic
• Decoding
• Execution and Memory Access

Macro Assembler

The macro assembler was written using flex and yacc. The goal was to produce an intuitive assembler. It allows C-style usage of assembly operations.

C/C++, Flex, Yacc-Sources for assembler and instruction set simulator. Assembler-Sources for example assembly programs.

Data memory initialization

• Zero initialized 32bit words:

word identifier[size]

• User initialized 32bit words: (size determined by assembler)

word identifier[]=word1,word2,word3,...

• User initialized 32bit words: (size determined by programmer)

word identifier[size]=word1,word2,word3,...

• String:

word identifier[]="string'"

• String: (size determined by programmer)

word identifier[size]="string'"

Data transfer

• Register-Register:

rXX = rYY

• Register-Memory and Memory-Register

rXX = rYY[disp]
rXX[disp] = rYY
Displacement values above zero are not possible with the current NORISK instruction-set.

• Register-Immediate

rXX = immediate
Immediate values can be numeric (0x for hexadecimal), labels or storage variables.

Arithmetic Operations

• Possible operations are &,|,^,<<,>>, <R< (rotate left), >R> (rotate right), >A> (arithmetic shift right)
• Syntax 1: rXX = rYY op rZZ
• Syntax 2: rXX op=rZZ

rXX is source and destination

• For some operations (depending on the instruction set) immediate values instead of rZZ are possible.

Control flow

• Labels: identifier followed by :
• Branch: goto label
• Conditional branch: goto label if condition
• Flag conditions: carry, !carry, zero, !zero
• Compare conditions: rXX {< or <= or > or >= or == or !=} {rYY or immediate}
  

This type of conditions produce a CMP operation before the branch.

• Relative call: rcall label. Saves next PC in register 15 and performs a relative jump.
• Return: return

Example program: bubble-sort

word test[]={20,20,21,19,15,1,10,12,6,7,3,100, 99,98,97}

r5 = sizeof(test)
r5 = r5+r0  ; calculate end

outer_loop:
r1 = test ; memory address of 1st operand
r2 = test ; memory address of 2nd operand
r2 += 1
r6 = 0  ; flag if sort is completed

inner_loop:
r3 = r1[0] ; load operands
r4 = r2[0]

goto next if r3 <= r4 ; decide whether it is necessary to swap them
r2[0] = r3 ; swap elements
r1[0] = r4
r6 += 1    ; set not-done flag

next:
r1 += 1
r2 += 1 ; next index
goto inner_loop if r2 < r5 ; repeat if end not reached
goto outer_loop if r6 != 0 ; repeat if sort not finished

r0 = 0x80000000 ; IO-address for leds
r1 = 0xF
r0[0] = r1 ; illuminate four leds

infinite:
goto infinite ; loop forever

Call Parameters

ass prgm_file bin_out [bin_data_out]

• prgm_file is the source code file
• bin_out is the binary code output
• bin_data_out is the binary data output. If this parameter is omitted, a default value (based on the bin_out parameter) is used.

Instruction Set Simulator

Call Parameters

iss prgmmem datamem [datamem_out]

• prgmmem is the filename of assembly program code output
• datamem is the filename of assembly data output
• datamem_out is optional. If specified the contents of the data memory after quit are written to that file.

During Operation

• Enter executes next instruction
• Sometimes IO input is requested (prompt: [IO@ address]:) the value specified is returned for this load operation. 0x for hexadecimal is allowed.
• q stops execution and writes data file

On chip-memory programmer

Visual C++ Source for Programmer using a serial com port.

Console operation

• programmer com_port_number con

Sends input from keys to the serial interface and displays received data.

Read memory

• programmer com_port_number read {prgm|data} file number_of_words

Reads first number_of_words words of program or data memory and writes file.

Write specific memory

• programmer com_port_number write {prgm|data} file [max_number_of_words]

Writes a maximum of max_number_of_words words of program or data memory from file. If max_number_of_words is omitted it writes the whole file.

Write whole program

• programmer com_port_number writeall basename

Writes basename.mif to program memory and basename_data.mif to data memory. escort bayan escortbayan