HD66717 Datasheet, PDF (76/90 Pages) Hitachi Semiconductor – (Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver)

HD66717
Standby Mode
Setting the standby mode bit (STB) to 1 puts the HD66717 in standby mode, where the device stops
completely, halting all internal operations including the R-C oscillator, thus further reducing current
consumption compared to that in sleep mode. Specifically, character and segment displays, which are
controlled by the multiplexing drive method, are completely halted. Here, all the SEG (SEG1 to SEG60)
and COM (COM4 to COM34) pins output the V_CC level, resulting in no display. If the AMP bit is set to 0
in standby mode, the LCD drive power supply can be turned off.
Annunciators can be displayed simply by supplying an approximately 40-Hz alternating signal for the
LCD drive signals to the EXM pin externally. If annunciator display is unnecessary during standby mode,
the EXM pin must be fixed to the V_CC or GND level and the annunciator display-on bit (DA) set to 0.
During standby mode, no instructions can be accepted other than those for annunciator display and the
start-oscillator instruction. To cancel standby mode, issue the start-oscillator instruction to stabilize R-C
oscillation before setting the STB bit to 0.
Figure 45 shows the procedure for setting and cancelling standby mode.
Turn off the LCD power supply: AMP = 0
Set standby mode: STB = 1
Supply an external alternating signal to the EXM pin
Standby mode (only annunciator display is available)
Issue the start-oscillator instruction
Wait at least 10 ms
Cancel standby mode: STB = 0
Turn on the LCD drive power supply: AMP = 1
Only for annunciator display;
set the DA bit to 0 when
annunciator display is not necessary.
Figure 45 Procedure for Setting and Cancelling Standby Mode
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