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TM4C123GH6PZ: LM4F232H5QC

Alam
Prodigy 120 points

Part Number: TM4C123GH6PZ

Hi, I am trying to Interface 20x4 lcd with TM4C123GH6PZ and  for it to work I need delay in nano seconds, referred to the Data Sheet of 20x4.

Please tell me how to calculate delay in nano seconds , because I'm new to TM4C123X

thanks

regards

Alam

  • 0
    Guru 117855 points

    A 20x4 (more usually referred to as "4x20") specifies such "nS" most (always & only) as, "Relative Edge Timings" between key/critical signal edges.  Note too - such "nS" timings are "minimums" - not maximums - thus there is NO necessity for you to "struggle" in meeting the specification's intention.

    The most usual occurrence of these "nS" mentions are at the signal edges between "R/W" and "E" and there is a less strict (yet still nS) spec for the "E" signal's width.      To you - in the "real world" - this means that you must,  "NOT TOGGLE" both "R/W" & "E" together - via a single MCU instruction."    (which is sure to violate "R/W & E" set-up and/or hold times)     Simply employ 2 (or more) instructions...

    Here - a brief example:

    • Set R/W (as appropriate - to write to or read from the display)
    • Apply stable (likely latched) Data from MCU Port to LCD Bus
    • Now set "E" high.   
    • Delay such as to comply w/Lcd's spec for "E" signal's minimum width.   (usually ~200-450nS)  
    • Now clear "E" (set low)

    This procedure completely eliminates the need for those delays "less than" 100nS.      (for most MCUs - running at "reasonable" speeds)

    A too narrow "E" pulse (time high) may "not be seen nor felt" by the Lcd module.    There is no penalty (beyond longer write times to the Lcd) for exceeding the duration of  "E signal high."    

    As illustrated - nS delays may be avoided - easing & speeding your development task...

    Poster makes no mention of the "great necessity to comply w/LCD's semi-demanding "initialization."   (Required!)    Also - it is usually helpful to employ a "pot" - driving pin "Vo" - able to span Gnd & Display's supply.     Usually the MCU's 3V3 outputs will be accepted by such Lcds - yet not always - caveat emptor...     (Lcd properly intended for 3V3 levels - makes great sense!)

    It should be noted that the post's Subject Line has been (essentially) muted - I responded (only) due to the mention of  LX4Fxyz - (some) effort should be made to "signal" post's content!