FRM010 serial chip

I have used a number of these chips with excellent results.

Soldering up the last board i suddenly thought WHY .......

The data sheet indicates pin 18 ( yes it uses pins ) to be connected to LCD power ( pin 2 ) - NB DO NOT Connect to +5v. Why?

Does this only apply to the Rev-Ed LCD module, or all similsr LCDs? After all not everybody uses the serial chip do they.

The LCD is powered by the PIC. This allows the PIC to manually reset (remove/reconnect) power to the LCD.

The "do not connect to +5V" is an instruction not to connect +5V to pin 18. LCD's can be powered from +5V in general or from pin 18 for a FRM010.

As to why the LCD is powered from pin 18 I'd guess that's so the FRM010 can power cycle the LCD to ensure a, good and clean, known reset state.

From Data Sheet.http://www.rev-ed.co.uk/docs/FRM010.pdf

"Note that the +5V supply is NOT directly connected to the LCD module as the LCD
is powered via pin 18 of the firmware chip."

I would have thought that this is simply to allow the firmware chip to switch the LCD on-off under your software control. i.e. a power switch - albeit a very low power switch.

As this would appear to be a PIC o/p assigned pin then never connect 5V supply to pin18.

You'll probably find that if you really want permanent power to the LCD then the LCD could directly accept the same 5V as the FRM010 - as long as you leave pin 18 n/c. But leaving the firmware to power it up and then initialise makes more sense.

Thank you all. Now understand, and it all makes good sense.

R.

I would have thought that this is simply to allow the firmware chip to switch the LCD on-off under your software control. i.e. a power switch - albeit a very low power switch.

Click to expand...

Thank raises the question, which are the commands to turn the +5V on and off at FRM010 pin 18?

As per the FRM010 datasheet:
254, 10 Turns visual LCD screen off via LCD standard control (for LED008 for example)
254, 14 Turns visual LCD screen (and cursor) on via LCD standard control

and maybe . . .
aaaa,xxxx Powers down the LCD
bbbb,yyy Powers up the LCD

If so, can we please be enlightend as the the values for aaa, bbb, xxx and yyy

Or

does the LCD power up/down only function automatically via a FRM010 Reset on pin 4

There is no such user command. It is a a feature only used internally by the firmware.

Technical,

Thanks for the confirmation