T6963C LCD - Can I fix /CE?

Discussion in 'General Electronics Chat' started by lithium, Mar 17, 2010.

  1. lithium

    Thread Starter New Member

    Jan 27, 2008
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    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.
     
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    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.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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  4. lithium

    Thread Starter New Member

    Jan 27, 2008
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    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
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    You can use the Shift1 for the outputs to the LCD, and use individual uC pins for the status reads.
     
  6. lithium

    Thread Starter New Member

    Jan 27, 2008
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    But the status is output on the data lines as well.
     
  7. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    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.
     
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