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.

3 Operands
Name	OpCode	Operands	Note	Decoding
ADD	0000	ddddrrrraaaa	D = R + A;	00000
ADC	0001	ddddrrrraaaa	D = R + A + C	00001
SUB	0010	ddddrrrraaaa	D = R - A	00010
SBC	0011	ddddrrrraaaa	D = R - A - c	00011
AND	0100	ddddrrrraaaa	D = R and A	00100
OR	0101	ddddrrrraaaa	D = R or A	00101
CMPI	0110	rrrriiiiiiii	R - I => flags	10000
XOR	0111	ddddrrrraaaa	D = R xor A	00110
LDB0	1000	rrrriiiiiiii	R(31~8) = 0, R(7~0) = I	01000
LDB1	1001	rrrriiiiiiii	R(31~16) = 0, R(15~8) = I	01001
LDB2	1010	rrrriiiiiiii	R(31~24) = 0, R(23~16) = I	01010
LDB3	1011	rrrriiiiiiii	R(31~24) = I	01011
RJMP	11000	iiiiiiiiiii	PC = PC + I	100xx (not 10000)
RCALL	11001	iiiiiiiiiii	R15 = PC; PC = PC + I	100xx (not 10000)
BRNE	11010	iiiiiiiiiii	if(!zero) PC = PC + I	100xx (not 10000)
BREQ	11011	iiiiiiiiiii	if(zero) PC = PC + I	100xx (not 10000)
BRCC	11100	iiiiiiiiiii	if(!carry) PC = PC + I	100xx (not 10000)
BRCS	11011	iiiiiiiiiii	if(carry) PC = PC + I	100xx (not 10000)

Two Operands

All 4-bit immediate values are unsigned.

2 Operands (2 instructions available)
Name	OpCode	Operands	Note	Decoding
ADDI	11110000	rrrriiii	R = R + I	00000
ADCI	11110001	rrrriiii	R = R + I + C	00001
SUBI	11110010	rrrriiii	R = R - I	00010
SBCI	11110011	rrrriiii	R = R - I - C	00011
LSL	11110100	rrrrssss	R <<= S	01110
ASL	11110101	rrrrssss	R >>>= S	01111
CMP	11110110	rrrraaaa	R = A => zero flag	10000
	11110111
ROL	11111000	rrrrssss		01100
ROR	11111001	rrrrssss		01101
ST	11111010	ddddaaaa	[A] = D	100xx (not 10000)
LD	11111011	ddddaaaa	D = [A]	11xxx
LSLI	11111100	rrrriiii	R <<= I	01110
ASRI	11111101	rrrriiii	R >>>= I	01111
MOV	11111110	ddddssss	D = S	10101
	11111111

One Operand

1 Operand (9 instructions available)
Name	OpCode	Operand	Note	Decoding
JMP	111111110000	rrrr	PC = R
CALL	111111110001	rrrr	PC => [SP], SP--, PC = R
PUSH	111111110010	rrrr	R => [SP], SP--
POP	111111110011	rrrr	SP++, [SP] => R
NEG	111111110100	rrrr	R = -R	10101
COM	111111110101	rrrr	R = not R	00111
PAR	111111110110	rrrr	1s in R
	111111110111

Non Operand

0 Operand (3 instructions available)
Name	OpCode	Note	Decoding
RET	1111111111110000	SP++, [SP] => PC
RETI	1111111111110001
CLI	1111111111110010	Interrupt flag = 0
SEI	1111111111110011	Interrupt flag = 1
SKIPCC	1111111111110100
SKIPCS	1111111111110101
SKIPNE	1111111111110110
SKIPEQ	1111111111110111
SKIPNO	1111111111111000
SKIPOV	1111111111111001
SKIPNOTNEG	1111111111111010
SKIPNEG	1111111111111011
	1111111111111100
	1111111111111101
	1111111111111110
NOP	1111111111111111		100xx (not 10000)

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.