HD44780 Clock Speed


New member

I bought an CFAH2002AYMCJP module a few years back which I retired when I bought my CF633.

I am putting together a Z80 based system and am looking at using the old LCD as a display for it.

The Z80 is clocked at 8Mhz, I am setting the module up as a Port-IO device and was wondering if the module would like being driven on an 8Mhz system.

I am asking because of a refrence in the HD44780U datasheet that reads... ' Correspond to high speed MPU bus interface - 2 MHz (when VCC = 5V) '

Oh, also is the 'E' pin active HIGH or LOW? I cant work out the H,H->L thing in the datasheet

Robert Heffernan
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Last edited:

CF Mark

The enable pin is active low.

As for the speed, you should really use the busy flag to check when you can write again.