[En-Nut-Discussion] Meaning of the EEMU signal

[Matthias]

Hello Harald,

>In fact EEMU(A15) is held high during EEPROM emulation,
>which indeed disables the RAM. If your board works
>without using this line, fine. :-) But

>     NICOUTB(NIC_CR, NIC_CR_STP | NIC_CR_RD2 | NIC_CR_PS0 | NIC_CR_PS1);
>     NICOUTB(NIC_PG3_EECR, NIC_EECR_EEM0);

>accesses the RTL8019 and I wonder how this should
>work if A15 is floating.


I speak about nicrtl.c v1.8 from Nut/OS 3.9.2.

Both NICOUTB commands are called BEFORE bit 5-7 of the address bus is 
disabled. (used as port pins).
And therefore the EEMU line is IMHO not needed, and therefore it works at my 
ethernut 1.3G board.


Maybe the EEMU is needed if the compiler use the external SRAM for variables 
or for the stack.
(I use the eeprom emulation routine without Nut/OS / Nut/Net.)


Best regards

Matthias