71M6521DE/71M6521FE
Energy Meter IC
DATASHEET
JANUARY 2008
Connecting LCDs
The 71M6521DE/FE has a LCD controller on-chip capable of controlling static or multiplexed LCDs. Figure 32 shows the basic
connection for a LCD.
6521
LCD
segments
commons
Figure 32: Connecting LCDs
The LCD segment pins can be organized in the following groups:
1. Nineteen pins are dedicated LCD segment pins (SEG0 to SEG18).
2. Four pins are dual-function pins CKTEST/SEG19, E_RXTX/SEG38, E_TCLK/SEG33, and E_RST/SEG32.
3. Twelve pins are available as combined DIO and segment pins SEG24/DIO4 to SEG31/DIO11 and SEG34/DIO14 to
SEG37/DIO17)
4. The QFN-68 package adds the three combination pins SEG39/DIO19 to SEG41/DIO21.
The split between DIO and LCD use of the combined pins is controlled with the DIO register LCD_NUM. LCD_NUM can be
assigned any number between 0 and 18. The first dual-purpose pin to be allocated as LCD is SEG41/DIO21 (on the 68-pin
QFN package). Thus if LCD_NUM=2, SEG41 and SEG 40 will be configured as LCD. The remaining SEG39 to SEG24 will be
configured as DIO19 to DIO4. DIO1 and DIO2 are always available, if not used for the optical port.
Note that pins CKTEST/SEG19, E_RXTX/SEG38, E_TCLK/SEG33, and E_RST/SEG32 are not affected by LCD_NUM.
Table 62 and Table 63 show the allocation of DIO and segment pins as a function of LCD_NUM for both package types.
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