mina32.rst

MINA32 Base Integer Instruction Set, Version 1

The following sections describe version 1 of the MINA32 base integer ISA.

Overview

MINA32 has a total of 27 registers:

• 24 32-bit general-purpose registers.
• 2 system registers.
• user-visible 32-bit program counter.

General-purpose registers r0-r7 are shared across all modes, r8-r15 are mode-specific.

Note

r15 is used as a stack pointer (SP) for instructions that use the stack. At all other times you can treat r15 as a general-purpose register.

Note

It is possible to access User mode registers r8_usr-r15_usr from Supervisor mode through the use of special move instructions.

The two system registers are MCR - the Machine Control Register - and FRET - the Fault Return Address register. While limited MCR access is possible in User mode, FRET is only visible to Supervisor mode threads.

The user-visible program counter (PC) holds the address of the currently executing instruction.

Fault Entry And Exit

MINA faults are handled as follows:

1. Depending on the fault cause, FRET is loaded with PC or PC + 4.
2. MCR is left-shifted by 32. ID is pulled high, MODE is set to 10 (Supervisor).
3. CAUSE is loaded with an appropriate fault code.
4. In case of a user-generated fault, COMMENT is loaded with a user-defined 8-bit value.
5. PC is set to 0.

To return from a fault, a fault handler must use the SWITCH instruction. SWITCH restores MCR by right-shifting it by 32 and resets PC to the value stored in FRET.

Instruction Formats

There are five core instruction formats (S/I/M/F/B). Instructions must be aligned on a four-byte boundary; misaligned instructions generate Misaligned Load Address faults.

The S-type (Standard) format is used for most instructions that operate on registers.

Figure 2: S-type Format

The I-type (Immediate) format is the default register-immediate format. An I-type immediate is sign-extended 12-bit data (IMM[11:0]) left-shifted by the shift amount specified in SHIFT.

Figure 3: I-type Format

The M-type (Move) format is a special register-immediate format. An M-type immediate is zero-extended 16-bit data (IMM[15:0]) left-shifted by 0 (MOVL instruction) or 16 (MOVU instruction).

Figure 4: M-type Format

The F-type (Funnel Shift) format is a special register-register format with four register operands.

Figure 5: F-type Format

The B-type (Branch) format is a special immediate format. A program counter-relative branch offset is sign-extended 24-bit data (IMM[23:0]) left-shifted by 2.

Figure 6: B-type Format

Instruction Summary

Arithmetic/Divide/NOP Group (0000)

Opcode	Mnemonic	Instruction	Format
0000	ADDI	Add Immediate	I
0001	MULTI	Multiply Immediate	I
0010	DIVI	Divide Immediate	I
0011	REMI	Compute Remainder Immediate	I
0100	SLTI	Set If Less Than Immediate	I
0101	SLTIU	Set If Less Than Immediate Unsigned	I
0110	NOP	No Operation	I
0111	PCADDI	Add Program Counter Immediate	I
1000	ADD	Add Register	S
1001	MULT	Multiply Register	S
1010	DIV	Divide Register	S
1011	REM	Compute Remainder Register	S
1100	SLT	Set If Less Than Register	S
1101	SLTU	Set If Less Than Register Unsigned	S
1110	SUB	Subtract Register	S
1111	PCADD	Add Program Counter Register	S

Logic/Bitwise Group (0001)

Opcode	Mnemonic	Instruction	Format
0000	ANDI	Logical AND Immediate	I
0001	ORI	Logical OR Immediate	I
0010	XORI	Logical XOR Immediate	I
0011	NANDI	Logical NOT-AND Immediate	I
1000	AND	Logical AND Register	S
1001	OR	Logical OR Register	S
1010	XOR	Logical XOR Register	S
1011	NAND	Logical NOT-AND Register	S
1100	POPCNT	Compute Population Count	S
1101	CLO	Count Leading Ones	S
1110	PLO	Find Position Of Leading One	S

Compare Group (0010)

Opcode	Mnemonic	Instruction	Format
0000	CMPI/EQ	Compare Equal Immediate	I
0001	CMPI/LO	Compare Lower Immediate	I
0010	CMPI/LS	Compare Lower Or Same Immediate	I
0011	CMPI/LT	Compare Less Than Immediate	I
0100	CMPI/LE	Compare Less Than Or Equal Immediate	I
1000	CMP/EQ	Compare Equal Register	S
1001	CMP/LO	Compare Lower Register	S
1010	CMP/LS	Compare Lower Or Same Register	S
1011	CMP/LT	Compare Less Than Register	S
1100	CMP/LE	Compare Less Than Or Equal Register	S

Register Branch Group (0011)

Opcode	Mnemonic	Instruction	Format
0000	RBRA	Register Branch, Immediate Offset	I
0001	RCALL	Register Call, Immediate Offset	I
0010	RET	Return From Subroutine Call	I
1000	ROBRA	Register Branch, Register Offset	S
1001	ROCALL	Register Call, Register Offset	S

Memory Group (0100)

Opcode	Mnemonic	Instruction	Format
0000	LD	Load Word, Immediate Offset	I
0001	LDH	Load Halfword, Immediate Offset	I
0010	LDB	Load Byte, Immediate Offset	I
0011	ST	Store Word, Immediate Offset	I
0100	STH	Store Halfword, Immediate Offset	I
0101	STB	Store Byte, Immediate Offset	I
0110	LDC	Load Machine Control Register	I
0111	STC	Store Machine Control Register	I
1000	RLD	Load Word, Register Offset	S
1001	RLDH	Load Halfword, Register Offset	S
1010	RLDB	Load Byte, Register Offset	S
1011	RST	Store Word, Register Offset	S
1100	RSTH	Store Halfword, Register Offset	S
1101	RSTB	Store Byte, Register Offset	S
1110	POP	Pop Word	S
1111	PUSH	Push Word	S

Move Group (0101)

Opcode	Mnemonic	Instruction	Format
0000	MOVI	Move Immediate	I
0001	MTI	Move If True Immediate	I
0010	MFI	Move If False Immediate	I
0011	MOVL	Move Lower Immediate	M
0100	MOVU	Move Upper Immediate	M
1000	MOV	Move Register	S
1001	SEL	Select Register	S
1011	MTOC	Move To Machine Control Register	S
1100	MFRC	Move From Machine Control Register	S
1101	MTOU	Move To User Mode Register	S
1110	MFRU	Move From User Mode Register	S

Shift Group (0110)

Opcode	Mnemonic	Instruction	Format
0000	LSL	Shift By Immediate, Logical Left	I
0001	LSR	Shift By Immediate, Logical Right	I
0010	ASR	Shift By Immediate, Arithmetic Right	I
0011	ROR	Rotate By Immediate, Right	I
1000	RLSL	Shift By Register, Logical Left	S
1001	RLSR	Shift By Register, Logical Right	S
1010	RASR	Shift By Register, Arithmetic Right	S
1011	RROR	Rotate By Register, Right	S
1100	FLSL	Funnel Shift, Logical Left	F
1101	FLSR	Funnel Shift, Logical Right	F

Control Group (0111)

Opcode	Mnemonic	Instruction	Format
0000	STOP	Shut Down Processor	I
0001	WFI	Wait For Interrupt	I
0010	SETT	Set T Bit	I
0011	CLRT	Clear T Bit	I
0100	SWITCH	Switch To Saved State	I
1000	SVCALL	Supervisor Call	S
1001	FAULT	Generate Fault	S
1010	MTOF	Move To Fault RetAddr Register	S
1011	MFRF	Move From Fault RetAddr Register	S
1100	MTOC2	Move To OMCR	S
1101	MFRC2	Move From OMCR	S

PC-Relative Branch Group (1000)

Opcode	Mnemonic	Instruction	Format
0000	BRA	PC-Relative Branch	B
0001	BT	PC-Relative Branch If True	B
0010	BF	PC-Relative Branch If False	B
1000	CALL	PC-Relative Call	B
1001	CT	PC-Relative Call If True	B
1010	CF	PC-Relative Call If False	B

Instruction Set

ADD (Add Register): Arithmetic Instruction

Figure 7: ADD

Assembler syntax: add dest, src1, src2

Description: Adds register src1 to register src2 and stores the result in register dest.

Operation:

ADD(src1, src2, dest)
{
    r[dest] = r[src1] + r[src2];
}

ADDI (Add Immediate): Arithmetic Instruction

Figure 8: ADDI

Assembler syntax: addi dest, src1, imm

Description: Adds shifted sign-extended 12-bit immediate imm[11:0] to register src1 and stores the result in register dest.

Operation:

ADDI(src1, imm, shift, dest)
{
    imm = exts12(imm) LSL shift;
    r[dest] = r[src1] + imm;
}

Note

Since the 12-bit immediate is sign-extended, this instruction can add and subtract immediate data.

AND (Logical AND Register): Logic Instruction

Figure 9: AND

Assembler syntax: and dest, src1, src2

Description: Logically ANDs register src1 with register src2 and stores the result in register dest.

Operation:

AND(src1, src2, dest)
{
    r[dest] = r[src1] AND r[src2];
}

ANDI (Logical AND Immediate): Logic Instruction

Figure 10: ANDI

Assembler syntax: andi dest, src1, imm

Description: Logically ANDs register src1 with shifted sign-extended 12-bit immediate imm[11:0] and stores the result in register dest.

Operation:

ANDI(src1, imm, shift, dest)
{
    imm = exts12(imm) LSL shift;
    r[dest] = r[src1] AND imm;
}