Thanks,

--BobG

-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On
Behalf Of G. Cadman
Sent: Thursday, August 09, 2001 5:55 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE] Interfacing a serial EEProm to a PIC16F877

Robert,

The /CS is require to invoke the writing sequence amongst other things, you
will
need to control it rather than tie it high.

Regards

Gary

"Robert E. Griffith" wrote:

> Hello,
>
> I am interfacing a MicroChip 25LC640P serial EEProm (SPI interface) to a
> PIC16F877.
>
> It is the only SPI device and I don't care about the hardware write
protect
> (it's not necessary is it?), so I would like to just tie off the CS\ (Chip
> Select), WP\ (write protect), and HOLD\ on the eeprom.
>
> However, the data sheet for the eeprom says that "After power-up, a high
to
> low transition on CS is required prior to any sequence being initiated."
Is
> there a simple way around connecting it to a PIC output just so that the
PIC
> can send it a pulse at start up? Is the 3-wire (SPI) interface really a
> 4-wire interface?
>
> Also, is the HOLD line of the eeprom necessary to connect?  I plan to use
> the MSSP on the 16F877 for the SPI interface.  Do you need to assert the
> HOLD line during interrupts so that the eeprom waits until the interrupt
is
> done? (assuming the MSSP is interrupted).
>
> And one more general question; If I tie HOLD\ and WP\ (and maybe CS\)
high,
> should I connect them to Vcc directly, or through a resistor?
>
> Thanks,
>
> --BobG
>
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