HD66717 Datasheet, PDF (73/90 Pages) Hitachi Semiconductor – (Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver)

HD66717
Partial-Display-Off Function
The HD66717 can program the number of display lines (NL1 and NL0 bits), divide the internal operating
frequency by four (OSC bit), and adjust the display contrast (CT bit). Combining these functions, the
HD66717 can turn off the second and/or subsequent lines, displaying only the characters in the first line
to reduce internal current consumption (partial-display-off function). This function is suitable for
calendar or time display, which needs to be continuous during system standby with minimal current
consumption. Here, the second to fourth non-displayed lines are constantly driven by the deselection level
voltage, thus turning off the LCD for the lines.
Note that internal clock frequency is reduced to a quarter, quadrupling execution time of each instruction;
MPU data transfer rate must be appropriately adjusted.
Table 26 lists partial-display-off function specifications and Figure 44 shows a sample display using the
partial-display-off function.
Table 26 Partial Display Off Function
Function Item
Normal 4-Line Display
Partially-Off Display
Character display
1st to 4th lines displayed
Only 1st line displayed
Segment display
Possible
Possible
Annunciator display
Possible
Possible
R-C oscillation frequency
160 kHz
160 kHz
Internal operating frequency
160 kHz (OSC = 0)
40 kHz (OSC = 1)
LCD single-line drive frequency 2.7 kHz (1/34 duty ratio)
0.7 kHz (1/10 duty ratio)
Frame frequency
78 Hz
66 Hz
Note: Select an optimum LCD drive voltage (between V_CC and V5) for the multiplexing duty ratio used,
using a reference voltage input pin (Vci) for the booster or the contrast-adjust bits (CT) .
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