SRAM

SRAM

Use a standard SPI SRAM memory device, as these devices share common command sets and memory structures.

Unlike EPD driver ICs, SRAM chips can usually handle high SPI clock speeds reliably — often up to 40MHz or even 100MHz.
How high you can actually push it depends on your specific hardware: PCB trace layout, parasitic capacitance, wire length if you're not on a clean board design, and similar physical factors that no datasheet number alone can guarantee for your particular setup.

My advice: start with software SPI, or a slow hardware SPI clock around 2MHz, and confirm it works correctly before raising the speed from there.

Here the situation is the opposite of the EPD display itself, where higher SPI speed buys you almost nothing.
With SRAM, a large volume of data moves between the chip and the MCU on every frame-buffer read or write, so clock speed directly affects how long that transfer takes — and there's real, meaningful time to be gained by pushing it higher.
Raise the speed incrementally until you hit the ceiling your specific board can reliably support; if you start seeing glitches or corrupted reads, back off one notch and stay there.

• EPD

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