Madsen, Jens wrote:
>
> Serial sampling with DRAM used for video sampling:
>
>       !4x sample clock
>       !                    256Kx8 DRAM-module
> *----------*                   *--------*
> !2044    A0!------------------>!/CAS    !
> !counter   !  *------------*   !        !
> !        A1!--! 20ns delay !-->!/RAS    !
> !          !  *------------*   !        !/--\
> !          !                   !  D0..D7!     Din/
> !          !                   !        !\--/ out
> !          !------------------\!        !
> !   A2..A10!                   !A0..A8  !
> !          !------------------/!     /WE!---- R/W
> !          !                   !     /OE!---- /OE
> *----------*                   *--------*
>
> Counter counts to 511*4. The memory contain 511*512 samples.
>
> Regards,
> Jens Dyejaer Madsen

The Idea is to use a 511 counter combined with the internal 512 counter.
This makes 511*512 = 261632 samples. Max clock is 7.6MHz with 70ns DRAM.
Minimum clock is 64KHz, but most LPT-ports handles more than 100KHz(486).
The counter may be asynchronous since the DRAM's contain internal latch.
The circuit is not complete but only to ilustrate that it is very simple
to use DRAM - and I think you need more components if you use SRAM.

Regards,
Jens Dyekjaer Madsen