UART Calculator

This is a simple calculator program that is used to test the basic functionality of the Mach-V processor. It contains all the basic instructiosn from RISC-V I and M extensions, and performs arithmetic operations based on user input via UART.

Source Code Organization

The source code for the UART Calculator is located in the sw/uart_calculator/ directory. The main source file is uart_calculator.c, which contains the implementation of the calculator logic and UART communication.

Porting Implementation

UART Output

As the calculator uses UART to communicate with the Mach-V processor, if the MMIO addresses are changed, the code in uart_calculator.c must be updated accordingly. The MMIO definitions are located at the top of the uart_calculator.c file,

#define MMIO_BASE 0xFFFF0000
#define UART_RX_VALID_OFF 0x00
#define UART_RX_DATA_OFF 0x04
#define UART_TX_READY_OFF 0x08
#define UART_TX_DATA_OFF 0x0C
#define SEVENSEG_OFF 0x80

Info

If you are using different MMIO addresses for UART or other peripherals, make sure to update these definitions accordingly.

DMEM Initialization

The application pre-loads data into Data Memory (DMEM) to test Load/Store instructions. This is handled via initialized global arrays in C, which the linker places in the .data section.

// Pre-loaded test patterns for Load operations
uint32_t test_data[4] = {
    0x12345678,
    0x9ABCDEF0,
    0xAABBCCDD,
    0xEEFF0011};

Build Configuration

There is nothing much to customize or change in the Makefile, ld.script and crt.s files for this application. This is also why this application can be regarded as a template for other new applications.

Application Usage

The calculator operates using a strictly defined 9-byte communication protocol over UART.

Communication Protocol

For every operation, the user must send exactly 9 bytes to the processor:

1. Command 1(1 Byte): An ASCII character selecting the operation (see table below).
2. Operand 1(4 Bytes): The first 32-bit argument, sent Big-Endian (MSB first).
3. Operand 2(4 Bytes): The second 32-bit argument, sent Big-Endian (MSB first).

Output: The result of the operation is written to the 7-segment Display MMIO address.

Command Reference

Category	Command	ASCII	Operation	Description
Arithmetic	ADD	a	op1 + op2	32-bit Addition
	SUB	s	op1 - op2	32-bit Subtraction
Logical	AND	c	op1 & op2	Bitwise AND
	OR	o	op1 | op2	Bitwise OR
	XOR	x	op1 ^ op2	Bitwise XOR
Shift	SLL	L	op1 << op2	Shift Left Logical
	SRL	R	op1 >> op2	Shift Right Logical
	SRA	A	op1 >> op2	Shift Right Arithmetic (sign-extended)
Comparison	SLT	l	op1 < op2	Set if Less Than (Signed)
	SLTU	u	op1 < op2	Set if Less Than (Unsigned)
Multiply / Div	MUL	m	op1 * op2	Low 32 bits of product
	MULH	H	op1 * op2	High 32 bits (Signed)
	MULHU	h	op1 * op2	High 32 bits (Unsigned)
	DIV	d	op1 / op2	Signed Division
	DIVU	D	op1 / op2	Unsigned Division
	REM	r	op1 % op2	Signed Remainder
	REMU	M	op1 % op2	Unsigned Remainder
Memory Access	LOAD	1..4	Mem[op1]	Reads from test_data. 1=LB, 2=LBU, 3=LH, 4=LHU
	STORE	5..6	Mem[op1] = op2	Writes to scratch_mem. 5=SB, 6=SH