Greetings,

I am working on a project involving a T6963C-based graphical LCD display. I am running somewhat low on pins on my MCU and I was wondering if it would be safe to tie /CE to ground permanently, since the data pins will be dedicated to the LCD on the MCU? The LCD still has a /RD pin that I would be able to use. I have the entire data sheet for the LCD and have searched online but have not found any similar problems.

Thanks.

 

The problem you will encounter is the direction (tristate control) on the Data lines will reverse with the /RD pin.

You cannot properly control the timing to write data and hold the data stable (from the MCU) at the end of the write without a conflict as the chip changes back to Read and the data out lines become active.

I remember seeing a 'cheat' approach to something like this, I think it was in the Sinclair ZX80? - add 1K resistors in series with the data lines, to prevent excessive current if both devices drive and have conflicting levels.

 

Take a look at Roman Black's Shift1 protocol page:
http://www.romanblack.com/shift1.htm

 

Thanks for your replies.

SgtWookie, this Shift1 system looks interesting but it appears like this is only useful for output-only pins. The T6963C _requires_ status reads to be performed before every command and in some cases several times during a command.

rjenkins, I would still have control over the /RD pin. At the end of the write I would just make /WR high (there are both /RD and /WR pins) and the LCD should tri-state the data lines. Or am I missing something?

This is my LCD: http://www.crystalfontz.com/product/CFAG12864D-STI-TZ

 

You can use the Shift1 for the outputs to the LCD, and use individual uC pins for the status reads.

 

But the status is output on the data lines as well.

 

Sorry, I only had a quick look at the data and thought I saw mention of a R/W line.

The seperate RD & WR take care of the data bus conflict, I'd give it a try.