FUJITSU Semiconductor Controller MB89950/950A - Manual (Page 248)

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CHAPTER 12 LCD CONTROLLER/DRIVER
12.1 Overview of LCD Controller/Driver
The LCD controller/driver includes 21 bytes of on-chip display data in memory, the
contents of which control an LCD via 42 segment and 4 common outputs. The function
can drive an LCD panel directly, using one of three selectable duty ratios.
■ LCD controller/driver function
The LCD controller/driver function displays the contents of a display data memory directly to the LCD
(Liquid Crystal Display) panel by segment and common outputs.
• LCD can be driven directly.
• Built-in voltage divider for LCD driving voltage. Can be connected to the external voltage divider.
• Up to 42 segment outputs (SEG0 to SEG41) and four common outputs (COM0 to COM3) may be used.
• Built-in display RAM: 21 bytes (42 x 4 bits)
• Three selectable duty ratios (1/2, 1/3, and 1/4). Not all duty ratios are available with all bias settings.
• SEG20 to SEG41 can be used as general-purpose port (option).
Table 12.1-1 "Bias and duty ratio combinations" shows the duty ratios available with various bias settings.
Note:
P00/SEG20 to P07/SEG27, P10/SEG28 to P17/SEG35 and P20/SEG36 to P25/SEG41
are set as N-ch open-drain I/O by mask option, they cannot be used as LCD segment output.
Table 12.1-1 Bias and duty ratio combinations
Bias
Duty ratio
1/2 duty ratio 1/3 duty ratio 1/4 duty ratio
1/2 bias X X
1/3 bias X
: Recommended mode
X: Do not use