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connect 632 or 634 to microcontroller


New member
hi, guys, I am trying to add one lcd displayer to my microcontroller(8051 based), and want to know if I can use 632 or 634. The microcontroller has UART port, that is like RXD and TXD, so what should I do? Just connect the ports to LCD and send characters to LCD? and send control ASCII character to do the controller of the LCD? Is it that simple?
Thanks a lot.
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CF Mark

The easiest way to connect to the LCD will be via the SPI port on the LCD.

If your mico doesnt have an SPI port, you can emulate one in software using the standard IO pins. Youll have to look around for information on how to do this though.

You can use the normal serial port of course, but you may then have to use a RS232 level converter IC which will take up extra PCB space and add cost.
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CF Tech

The 632 & 634 can take "logic level" RS-232 (0-5v swing). Just close "JPE", and connect your micro's Tx pin to the LCD's DATA_IN pin of connector J2.

Since most RS-232 level converters invert the signal, the UART pins of most micros are inverted from the actual RS-232 levels. If that is the case for your micro, then also close JPB, which will make the 632 or 634 look for an inverted serial stream.

SPI is also an option, but be sure to observe the maximum clock frequency (18KHz) for the 632/634 SPI interface.

This information is discussed in more detail in the 632 or 634 data sheet.


New member
quasi-spi ?

Why doesn't the C.F. 634 display have a Serial Data Out pin (or the equivalent) as the SPI protocol mandates?

SPI is a circular protocol, right, where data is sent and receivced simultaneously for built-in error checking. So where is the data output pin?

Phil Taylor

CF Tech

The display does not have any thing to say--it is a "write-only" device.

Other devices from other manufacturers also claim "Digital communication protocols include the SPIE, QSPIE, and MicrowireE standards." without implementing the data out line.

SPI can be thought of as circular, but the data returned is not necessarily an exact copy of the data sent. On a readable device (such as an ADC) the data returned must be different than what you sent, or you could not get information from it.
USB LCD Displays - Graphic and Character LCDs with a Keypad


New member
SPI and uC

Yeah, you're right. I am coming toward your LCD module with experience with SPI devices that are 'ganged' up such as Maxim6952. On these chips the output is exactly the input signal, with a delay, that feeds in series to all of the SPI devices in the chain. I suppose they implement it this way so that if the uC is several feet away, as in a large LED display, you're running half as much transmission line(?).

Something got me thinking that embedded hardware peripheral SPI ssp's did error checking. I guess they don't!

My mistake. Thanks for the help, CF.

Phil Taylor