ESP32 SPR

1 Overview

Speical Registers of ESP32 (Xtensa) hold the majority of the state added to the processor.

2 R/W SPR

 rsr.* a2
 wsr.* a2
 xsr.* a2      <--- exchanges the values in a General Register (GPR) and a Special Register (SPR)

For example:

rsr.prid a2

3 PRID

Processor ID

PRID on the ESP108 architecture (ESP32) :

• 0xCDCD on the PRO processor
• 0xABAB on the APP CPU

We can distinguish between the two by simply checking bit 1: It's 1 on the APP and 0 on the PRO processor.

void dump_prid()
{
    uint32_t pd;

    //asm volatile ("rsr %0, PRID" : "=r" (pd));
    asm volatile ("rsr.prid %0" : "=r" (pd));
    printf("prid = 0x%08X\r\n", pd);
}

4 CONFIG

void dump_configid()
{
    uint32_t c0, c1;

    //asm volatile ("rsr %0, CONFIGID0" : "=r" (c0));
    //asm volatile ("rsr %0, CONFIGID1" : "=r" (c1));
    asm volatile ("rsr.configid0 %0" : "=r" (c0));
    asm volatile ("rsr.configid1 %0" : "=r" (c1));

    printf("configid0 = 0x%08X\r\n", c0);
    printf("configid1 = 0x%08X\r\n", c1);
}