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ADE7169 数据表(PDF) 99 Page - Analog Devices |
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ADE7169 数据表(HTML) 99 Page - Analog Devices |
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99 / 144 page ![]() ADE7566/ADE7569/ADE7166/ADE7169 Rev. A | Page 99 of 144 Table 86. LCD Pointer SFR (LCDPTR, 0xAC) Bit Mnemonic Default Description 7 R/W 0 Read or Write LCD Bit. If this bit is set (1), the data in LCDDAT is written to the address indicated by the LCDPTR[5:0] bits. 6 RESERVED 0 Reserved. 5 to 0 ADDRESS 0 LCD Memory Address (see Table 89). Table 87. LCD Data SFR (LCDDAT, 0xAE) Bit Mnemonic Default Description 7 to 0 LCDDATA 0 Data to be written into or read out of the LCD Memory SFRs. Table 88. LCD Segment Enable 2 SFR (LCDSEGE2, 0xED) Bit Mnemonic Default Description 7 to 4 RESERVED 0 Reserved. 3 FP19EN 0 FP19 Function Select Bit. 0 = General-Purpose I/O, 1 = LCD function. 2 FP18EN 0 FP18 Function Select Bit. 0 = General-Purpose I/O, 1 = LCD function. 1 FP17EN 0 FP17 Function Select Bit. 0 = General-Purpose I/O, 1 = LCD function. 0 FP16EN 0 FP16 Function Select Bit. 0 = General-Purpose I/O, 1 = LCD function. LCD SETUP The LCD Configuration SFR (LCDCON, 0x95) configures the LCD module to drive the type of LCD in the user end system. The BIAS and LMUX[1:0] bits in this SFR should be set according to the LCD specifications. The COM2/FP28 and COM3/FP27 pins default to LCD segment lines. Selecting the 3× multiplex level in the LCD Configuration SFR (LCDCON, 0x95) by setting LMUX[1:0] to 2d changes the FP28 pin functionality to COM2. The 4× multiplex level selection, LMUX[1:0] = 3d, changes the FP28 pin functionality to COM2 and the FP27 pin functionality to COM3. LCD segments FP0 to FP15 and FP26 are enabled by default. Additional pins are selected for LCD functionality in the LCD Segment Enable SFR (LCDSEGE, 0x97) and LCD Segment Enable 2 SFR (LCDSEGE2, 0xED) where there are individual enable bits for the FP16 to FP25 segment pins. The LCD pins do not have to be enabled sequentially. For example, if the alternate function of FP23, the Timer 2 input, is required, any of the other shared pins, FP16 to FP25, can be enabled instead. The Display Element Control section contains details about setting up the LCD data memory to turn individual LCD segments on and off. Setting the LCDRST bit in the LCD Configuration SFR (LCDCON, 0x95) resets the LCD data memory to its default (0). A power-on reset also clears the LCD data memory. LCD TIMING AND WAVEFORMS An LCD segment acts like a capacitor that is charged and discharged at a certain rate. This rate, the refresh rate, determines the visual characteristics of the LCD. A slow refresh rate results in the LCD blinking on and off between refreshes. A fast refresh rate presents a screen that appears to be continuously lit. In addition, a faster refresh rate consumes more power. The frame rate, or refresh rate, for the LCD module is derived from the LCD clock, fLCDCLK. The LCD clock is selected as 2048 Hz or 128 Hz by the CLKSEL bit in the LCD Configuration SFR (LCDCON, 0x95). The minimum refresh rate needed for the LCD to appear solid (without blinking) is independent of the multiplex level. The LCD waveform frequency, fLCD, is the frequency at which the LCD switches the active common line. Thus, the LCD waveform frequency depends heavily on the multiplex level. The frame rate and LCD waveform frequency are set by fLCDCLK, the multiplex level, and the FD[3:0] frame rate selection bits in the LCD Clock SFR (LCDCLK, 0x96). The LCD module provides 16 different frame rates for fLCDCLK = 2048 Hz, ranging from 8 Hz to 128 Hz for an LCD with 4× multiplexing. Fewer options are available with fLCDCLK = 128 Hz, ranging from 8 Hz to 32 Hz for a 4× multiplexed LCD. The 128 Hz clock is beneficial for battery operation because it consumes less power than the 2048 Hz clock. The frame rate is set by the FD[3:0] bits in the LCD Clock SFR (LCDCLK, 0x96); see Table 83 and Table 84. The LCD waveform is inverted at twice the LCD waveform frequency, fLCD. This way, each frame has an average dc offset of zero. ADC offset degrades the lifetime and performance of the LCD. |
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