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wood_muzy
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Problem about Initialising instruction of character LCD screen on Spartan 3E starter kit

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Help!!

 

When Initialising the character LCD screen, 4-bit instructions 3,3,3,2 must be sent with suitable delays, Is there anyone who can tell me the meaning of the instructions 3,3,3,2 ? 

 

 Thanks!

Message Edited by wood_muzy on 11-04-2009 09:55 PM
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dclemmensen
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These are not "commands" at all: they (together with the delays betwee them) are a synchronization sequence, so they do not have separate individual meanings. The LCD device uses 8-bit commands, not 4-bit commands. When physically configured to use a 4-bit bus, each 8-bit command is sent as a pair of 4-bit "nybbles." But the device must have a way to figure out, after any reset of the device or the controllng circuit (the FPGA in our case), which nybble is the first nybble and which is the second nybble of the 8-bit command. The synchronization sequence does this, in effect, by waiting a very long time between nybbles. After the initialization sequence, the two nybbles of each 8-bit command are separated by a much shorter time. After initialization, you must wait only 1 microsecond between the two nybbles of the command, and in all but one case you must wait 40 microseconds after the second nybble of the command so the command can be executed. One particular command, the "clear" command, takes longer.

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dclemmensen
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Registered: ‎12-29-2007
These are not "commands" at all: they (together with the delays betwee them) are a synchronization sequence, so they do not have separate individual meanings. The LCD device uses 8-bit commands, not 4-bit commands. When physically configured to use a 4-bit bus, each 8-bit command is sent as a pair of 4-bit "nybbles." But the device must have a way to figure out, after any reset of the device or the controllng circuit (the FPGA in our case), which nybble is the first nybble and which is the second nybble of the 8-bit command. The synchronization sequence does this, in effect, by waiting a very long time between nybbles. After the initialization sequence, the two nybbles of each 8-bit command are separated by a much shorter time. After initialization, you must wait only 1 microsecond between the two nybbles of the command, and in all but one case you must wait 40 microseconds after the second nybble of the command so the command can be executed. One particular command, the "clear" command, takes longer.

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wood_muzy
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Thanks, dclemmensen!

 Your answer must be right, but I do not understand why the description about synchronization sequence can not find in the datasheet of ST766U.

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