PowerQUICC Processorsのトピックmtmsr[fp] do not follow sync

mtmsr[fp] do not follow sync

poloyellow — Thu, 29 Mar 2018 01:49:51 GMT

hi,

I had a test in mpc8640. I try to do mtmsr[fp] but forget the synchronizing instruction followed.

for example:

/****************************************/

mfmsr r3

rlwinm r3,r3,0,19,17 /*mask fp*/

ori r3,r3,0x1000 /* set ME*/

mtmsr r3

sync

ori r3,r3,0x2000 /* set fp, without sync followed*/

mtmsr r3

stfd f0, 48(r1)

/*********************************/

When I excute the code, the cpu seems do not enter any exception or interrupt, include machine check, and there isn't any response in serial port. So I don't know what the cpu is doing after the instruction 'stfd', and which state the cpu is in.

Can anyone give me any explanation?

Thanks.

Polo Yellow

Re: mtmsr[fp] do not follow sync

alexander_yakov — Tue, 03 Apr 2018 06:54:43 GMT

According to E600 Core Reference Manual:

"A context synchronizing instruction must follow an mtmsr instruction"

This is said explicitly in section Section 2.1.4.4 "Machine State Register (MSR)"

In this statement word "must", as per my personal understanding, means that violating this rule will lead to unpredictable results.

Have a great day,
Alexander
TIC

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