HD66724 Datasheet, PDF (99/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Standby Mode
Setting the standby mode bit (STB) to 1 puts the HD66724/HD66725 in the 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 the sleep mode. Specifically, character and segment displays,
which are controlled by the multiplexing drive method, are completely halted. Here, all the SEG (SEG1 to
SEG72 (96)) and COM (COM1 to COM24, COMS1/2) pins output the GND level, resulting in no display.
If the AMP bit is set to 0 in the standby mode, the LCD drive power supply can be turned off.
During the standby mode, no instructions can be accepted other than those for the start-oscillator
instruction and the key scan interrupt generation enable instruction. To cancel the standby mode, issue the
start oscillator instruction to stabilize R-C oscillation before setting the STB bit to 0.
Although key scan is halted in the standby mode, the HD66724/HD66725 can detect eight key inputs
connected with strobe signal KST0, thus generating key scan interrupt (IRQ*). This means, the system can
be activated from a completely inactive state. For details, refer to the Key Scan Interrupt (Wake-Up
Function) section.
Turn off the LCD power supply: AMP = 0
Set standby mode: STB = 1
Standby mode (Key scan interrupt enabled)
Issue the start-oscillator instruction
Wait at least 10 ms
Cancel standby mode: STB = 0
Turn on the LCD drive power supply: AMP = 1
Figure 58 Procedure for Setting and Canceling Standby Mode
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