xe8802 Semtech Corporation, xe8802 Datasheet - Page 152

• Manufacturer Part Number: xe8802
• Description: Data Acquisition Soc With 16+10 Bit Zoomingadc? Embedded Risc Controller And Lcd Driver
• Manufacturer: Semtech Corporation

The voltage generator has to be configured for the use of the internal reference (VgenRefEn=1 in RegVgenCfg0).
The generator has to run (VgenOff=0 and VgenStdb=0 in RegVgenCfg0). It has to multiply by 3 (VgenMode=0 in
RegVgenCfg0) and the generator output impedance is set to minimum (VgenClkSel=11 in RegVgenCfg0).
The LCD driver is set to direct drive (LcdMux=00 in RegLcdOn) and the waveform generator is enabled
(LcdSleep=0 in RegLcdOn). All pads are set into the LCD driver mode by setting all bits of register RegLcdSe to
1. To select a frame rate of about 50Hz, set the bits LcdFreq=00 and LcdDivFreq=100 in RegLcdClkFrame. Note
that the precision of the frame frequency depends on the selected clock source (see clock block documentation).
The 32 segments are on or off depending on the bits set in the registers RegLcdDataN. Only the bits 0 and 4 of
these registers are used in direct drive. All other bits are don’t care. Figure 19-3 shows the generated waveforms
for two segments. Segment0 is off (LcdData0[0]=0 in RegLcdData0) and segment1 is on (LcdData0[4]=1 in
RegLcdData0). The figure shows on the left side the waveforms on the circuit pins, in the middle the segment
status and on the right the voltage on the segment (difference between the pad_lcd_io pin and pad_lcd_com0 pin).
© Semtech 2006
pad_lcd_com0
pad_lcd_io[1]
pad_lcd_io[0]
V3
V0
V3
V0
V3
V0
Figure 19-3: Direct Drive mode waveforms
XE8802 Sensing Machine Data Acquisition MCU
19-8
with ZoomingADC™ and LCD driver
-V3
V0
V3
V0
pad_lcd_com0 - pad_lcd_io[0] (off)
pad_lcd_com0 - pad_lcd_io[1] (on)
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