Problem when writing software for Blackbox Rocc example

Hi, I encounter a problem when implementing the software design for the Rock BlackBox example. I tried to use the black box in software, and I write the code like the following. But it gives no response when I test with ./simualtion-XXX-XXXConfig XXX.riscv in verilator.

#include<stdio.h>
#include "rocc.h"

static inline void accum_write(int idx, unsigned long data)
{
	ROCC_INSTRUCTION_SS(3, data, idx, 0);
}

static inline unsigned long accum_read(int idx)
{
	unsigned long value;
	ROCC_INSTRUCTION_DSS(3, value, 0, idx, 1);
	return value;
}

static inline void accum_load(int idx, void *ptr)
{
	asm volatile ("fence");
	ROCC_INSTRUCTION_SS(3, (uintptr_t) ptr, idx, 2);
}

static inline void accum_add(int idx, unsigned long addend)
{
	ROCC_INSTRUCTION_SS(3, addend, idx, 3);
}

static inline unsigned long black_box(int num1, int num2)
{	
	unsigned long value;
	ROCC_INSTRUCTION_DSS(0, value, num1, num2, 1);
	return value;
}

unsigned long data = 0x3421L;

int main(void)
{
	unsigned long result;
	
	//Blackbox process
	black_box(1,2);
	black_box(3,4);
	result=black_box(5,6);
	printf("The result is:  %ld\n",result);
	printf("Blackbox Success!\n");
	
	accum_load(0, &data);
	accum_add(0, 2);
	result = accum_read(0);

	if (result != data + 2)
		return 1;

	accum_write(0, 3);
	accum_add(0, 1);
	result = accum_read(0);

	if (result != 4)
	{printf("Failed\n");
		return 2;}
	printf("Accum Success!\n");
	

	return 0;
}

But if I move the blackbox process below the Accum part, it works, which makes me very confused.

I do not where I am wrong, I am quite confused.

Could you give an example of how to use Blackbox.

Thanks in advance

Start by reproducing the supplied C program with the Rocket Chip BlackBox example under Verilator, comparing behavior when the BlackBox calls precede or follow the Accum calls. Determine the cause of the ordering-dependent lack of response and document a working BlackBox usage example, including the conditions that make the test complete successfully.