How to modify MSEL pin state?

HiFive1 Rev B
1

First, I read through this thread here on this:

Would like to know if any latest update on above. Like any ways to modify the MSEL pin states or any updated documentation?
(I am now referring to April 11, 2019 documentation corresponding to FE310-g002 manual.)

As per section 5 in above documentation, since MSEL pins states are NOT modifiable,
Can someone explain how & when the boot process jumps into FLASH or RAM ?

I see after power reset, the execution jumps into flash/ram, but could n’t understand how?

2

Hi Vincent,

The MSEL pins are fixed at 0x3 (they are not bonded out), and it looks like we still need to remove that table to avoid any further confusion. Thanks for pointing this out - we will get this fixed. I’ve dissected the boot flow a little bit more to demonstrate how it works:

Reset Vector ROM
0x1000: Holds MSEL "pins", value of 0x3 (pins are NOT bonded out)
0x1004: BOOT ENTRY POINT IS HERE:
    auipc t0, 0         // load t0 with PC (t0 = 0x1004)
    lw t1, -4(t0)       // load t1 with MSEL (t0 = 0x3, fixed)
    slli t1, t1, 0x3    // shift t1 left by 3. (t1 = 0x18)
    add t0, t0, t1      // t0 = t0 + t1 (t0 = 0x101C)
    lw t0, 252(t0)      // load t0 with value at 0x101C (t0 = 0x10000)
    jr t0               // jump to memory mapped Mask ROM ......

0x10000:
memory mapped Mask ROM (jumps to memory mapped OTP) 
    00010000: 0x732540f1   csrr    a0,mhartid               // a0 = 0
    00010004: 0x97050000   auipc   a1,0x0                   // a1 = 0x10004
    00010008: 0x93854505   addi    a1,a1,84 # 0x10058       // a1 = 0x10058
    0001000c: 0xb7020200   lui     t0,0x20                  // t0 = 0x20000
    00010010: 0x67800200   jr      t0 # 0x20000             // jump to 0x20000, memory mapped OTP

0x20000:
memory mapped OTP 
Run low level init and jump to QSPI location 0x20010000
3

HI David,

Thanks, that explains how execution jumps into rom (0x20010000) and start executing from.

But, I am not clear what “not bonded out” mean.
I am waiting for my FE310-G002 chips to arrive, would I be able to modify the MSEL pins state (pull up/down) in my PCB? or are these MSEL pins not even out of FE310-G0002 chip?

4

Not bonded out means that there is no physical connection from the die inside the package to the outside world. So the MSEL pins cannot be changed to a different value on this device.

5

Hi David,

Is there way to participate/correct in FE310 G002 manual documentation? (not for money though) I use this manual to work on my project too. Is it available in git?

6

Please ignore the MSEL table for now. We will work on getting the document updated (it is an internal doc).

7

The FE310 G002 manual has been updated to remove the MSEL table, and now describes the boot flow is fixed. Please see [this] link.

8

Cool. I see the mstatus.MPIE is also fixed. Thanks !