HD66727 Datasheet, PDF (85/97 Pages) Hitachi Semiconductor – Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver with Key Scan Function

HD66727
Sleep Mode
Setting the sleep mode bit (SLP) to 1 puts the HD66727 in the sleep mode, where the device halts all the
internal display operations except for annunciator display and key scan operations, thus reducing current
consumption. 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 (COM1 to COM34) pins
output the V_CC level, resulting in no display. If the AMP bit is set to 0 in the sleep mode, the LCD drive
power supply can be turned off, reducing the total current consumption of the LCD module.
Annunciators can be normally displayed in the sleep mode. Since they are driven at logic operating power
supply voltage (V_CC – AGND), they are available even if the LCD power supply is turned off (AMP = 0).
This function allows time and alarm marker indication during system standby with reduced current
consumption.
During the sleep mode, no instructions can be accepted for character/segment display and neither DDRAM,
CGRAM, nor SEGRAM can be accessed.
The key scan circuit operates normally in the sleep mode, thus allowing normal key scan and key scan
interrupt generation. All keys can be scanned while only displaying annunciators. For details, refer to the
Key Scan Control section.
Table 38 compares the functions of the sleep mode and standby mode.
Table 38 Comparison of Sleep Mode and Standby Mode
Function
Character display
Segment display
Annunciator display
Sleep Mode (SLP = 1)
Turned off
Turned off
Can be turned on
R-C oscillation
Key scan
Operates normally
Can operate normally
Standby Mode (STB = 1)
Turned off
Turned off
Can be turned on when an alternating signal
is supplied to the EXM pin
Halted
Halted but IRQ* can be generated
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