More chip selects

Hello all,

I have a CPU board which has a M16C/62P microcontroller and the
microcontrollers
three CS pins are connected to SRAM, EEPROM and ADC.
Now I need to add LCD to the CPU board throuch the latch and I will
need
one more CS pin to the latch.

I am thinking to expand one of the microcontrollers CS pin to get two
CS pins using address decoder in a way that this microcontrollers CS
pin comes to the
address decoder and based on address it selects one of the two CS
pins.

Is there other possibilities mayby to expand CS pins?

jtp wrote:
> Hello all,
>
> I have a CPU board which has a M16C/62P microcontroller and the
> microcontrollers three CS pins are connected to SRAM, EEPROM and ADC.
> Now I need to add LCD to the CPU board throuch the latch and I will
> need one more CS pin to the latch.
>
> I am thinking to expand one of the microcontrollers CS pin to get two
> CS pins using address decoder in a way that this microcontrollers CS
> pin comes to the address decoder and based on address it selects one
> of the two CS pins.
>
> Is there other possibilities mayby to expand CS pins?

Doesn't sound like a homework problem to me, so I'll take a stab:

Address decoding, the method that you describe, is the most common.
And probably second most common would be indirect access, where you
control which block or device gets the CS by way of writing to a
control bit somewhere - for example: some sort of writable register on
your data bus (which would need its own address decoding unless you
have an unused data bit), or using a GPIO line, if one is available.

   Marc

GPIO = general purpose I/O