Author Topic: CPU registers - emulated or real?  (Read 763 times)

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Offline Jane

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CPU registers - emulated or real?
« on: November 01, 2015, 01:56:10 am »
I started recently playing with a MIPS CPU( made by Broadcom). As far as I know it allows to use a Broadband Studio to communicate with that CPU.
That MIPS CPU has  Read/Write registers. I can write to these registers and in the Broadband studio I can see the new value was written. But if I restart mainboard, that uses the  MIPS CPU, there is the previous value before I changed it.
Do you think the Broadband studio only emulates those registers and I write to not the real registers?
I used a logic analyzer to check how  the Broadband studio writes to registers.
It does write to CPU but the address is different than a documentation says.
For example
Address Offset = 32'h001a_00d8
Physical Address = 32'h101a_00d8

but I can not see that address during sniffing with a logic analyzer
Any idea?


Offline Paul Price

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Re: CPU registers - emulated or real?
« Reply #1 on: November 01, 2015, 03:30:10 am »
The upper address bit is probably ignored in decoding the address of the registers for reading and writting.

The registers are probably not reset when you restart the mainboard, so the previous values remain.

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