Nano Processor Instruction Manual

1. Overview

The nano processor executes 12-bit instructions stored in a program ROM. Each instruction is decoded by the instruction decoder and controls the datapath, register bank, arithmetic logic unit (ALU), and program flow.

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2. Instruction Format

Each instruction is 12 bits wide and structured as follows:

Bits	Field Name	Description
11	Load_Select	1: Immediate mode, 0: Register/ALU operation
10	Add_Sub_Select	1: SUB/NEG/JZR, 0: ADD/MOVI
9..7	R_A / Dest_Reg	Register A / Destination Register
6..4	R_B_Select	Register B / Source Register
3..0	Imd_Val / Addr	Immediate value or Jump address

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3. Instruction Set

Mnemonic	Binary Pattern	Description
MOVI Rd, Imm	1 0 ddd xxx iiii	Move immediate value iiii to register ddd
NEG Rd	0 1 ddd xxx 0000	Negate the value in register ddd
ADD Rd, Rs	0 0 ddd sss 0000	Add register sss to ddd
SUB Rd, Rs	0 1 ddd sss 0000	Subtract sss from ddd
JZR Rc, Addr	1 1 ccc xxx aaaa	If Rc == 0, jump to address aaaa
END	1 1 000000000000	Halt the program (by convention)

Legend:

• ddd = destination register (R0–R7)
• sss = source register (R0–R7)
• iiii = 4-bit immediate value
• aaaa = 4-bit jump address

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Example Instructions from ROM

Address	Instruction	Binary	Description
0	MOVI R7, 10	101110000010	R7 ← 10
1	MOVI R2, 1	100100000001	R2 ← 1
2	NEG R2	010100000000	R2 ← -R2
3	ADD R7, R2	001110100000	R7 ← R7 + R2
4	JZR R7, 7	111110000111	If R7 == 0, jump to address 7
5	JZR R0, 3	110000000011	If R0 == 0, jump to address 3
6	JZR R1, 7	111110000111	If R1 == 0, jump to address 7
7	END	110000000000	Halt the program

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4. Reset Function

The reset button is mapped in basys3.xdc.

Functionality:
Pressing the reset button (connected to pin U18) resets the processor, clears all registers, and restarts execution from instruction 0 in ROM.

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5. Output Signals

Output Signal	Description
Cathode_7Seg	Displays the value of R7 on the 7-segment display
overflow	Indicates if arithmetic overflow has occurred
zero	Set when the result of an operation is zero

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6. Example Usage

To begin program execution:

1. Press the reset button (pin U18).
2. The processor will fetch and execute instructions sequentially from ROM.
3. R7’s value will be visible on the 7-segment display.
4. Status outputs overflow and zero will update according to operations.