How do I connect 8 Flash memories to a bus?

[socketz]

I have eight M58LW064D flash memory chips, they are 8 megs each for a total of 64 Megs.

The M58LW064D datasheet is here:
www.st.com/stonline/books/pdf/docs/8938.pdf

I have a 16 bit data bus in my mcu, and, as I stated, I need to connect 8 of these chips to the data bus.

The M58LW064D has 22 address lines in 16 bit mode, and 3 enable lines.
Page 11 of the datasheet contains the 3 enable lines truth table.

I obviously have 3 more address lines than the chips, but instead of using a 3 to 8 decoder, I know I can just use the enable lines in the flash memories.

The problem is I don't know how to connect the 3 address lines to the 3 enable lines. It's pretty obvious that it's not a 1 to 1 connection because the 3 address lines in 0 would enable ALL the chips, and I need only 1 to be enabled at a time.

Can you help?

Thanks.

 

[bobcat1]

You Need to use address decoder

You can design custom one using CPLD from xilinx cypress or altera

any other method involved using glue logic like hc138/139 etc


best


bobi

 

[cube007]

Hello,

perhaps you will also need additional bus drivers because 8 devices are a not a little load. This depends on all devices which are working on the bus and if they have enough power (current) to drive the signals.

Bye,
cube007