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HT56R22 数据表(PDF) 60 Page - Holtek Semiconductor Inc |
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HT56R22 数据表(HTML) 60 Page - Holtek Semiconductor Inc |
60 / 127 page HT56R22/HT56R23/HT56R24/HT56R25/HT56R26 Rev. 1.30 60 December 26, 2014 Analog to Digital Converter The need to interface to real world analog signals is a common requirement for many electronic systems. However, to properly process these signals by a microcontroller, they must first be converted into digital signals by A/D converters. By integrating the A/D con- version electronic circuitry into the microcontroller, the need for external components is reduced significantly with the corresponding follow-on benefits of lower costs and reduced component space requirements. A/D Overview The device contains an 8-channel analog to digital con- verter which can directly interface to external analog sig- nals, such as that from sensors or other control signals and convert these signals directly into either a 12-bit dig- ital value. The accompanying block diagram shows the overall in- ternal structure of the A/D converter, together with its as- sociated registers. A/D Converter Data Registers - ADRL, ADRH The device, which has an internal 12-bit A/D converter, requires two data registers, a high byte register, known as ADRH, and a low byte register, known as ADRL. After the conversion process takes place, these registers can be directly read by the microcontroller to obtain the digit- ised conversion value. Only the high byte register, ADRH, utilises its full 8-bit contents. The low byte regis- ter utilises only 4 bit of its 8-bit contents as it contains only the lowest bits of the 12-bit converted value. In the following table, D0~D11 is the A/D conversion data result bits. Register Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 ADRL D3 D2 D1 D0 ¾¾¾¾ ADRH D11 D10 D9 D8 D7 D6 D5 D4 A/D Data Registers A/D Converter Control Registers - ADCR, ACSR, ADPCR To control the function and operation of the A/D con- verter, three control registers known as ADCR, ACSR and ADPCR are provided. These 8-bit registers define functions such as the selection of which analog channel is connected to the internal A/D converter, which pins are used as analog inputs and which are used as normal I/Os, the A/D clock source as well as controlling the start function and monitoring the A/D converter end of con- version status. The ACS2~ACS0 bits in the ADCR register define the channel number. As the device contains only one actual analog to digital converter circuit, each of the individual 8 analog inputs must be routed to the converter. It is the function of the ACS2~ACS0 bits in the ADCR register to determine which analog channel is actually connected to the internal A/D converter. The ADPCR control register contains the PCR7~PCR0 bits which determine which pins on PA7~PA0 are used as analog inputs for the A/D converter and which pins are to be used as normal I/O pins. If PCR7~PCR0 has a value of ²11111111², then all eight pins, namely AN7~AN0 will all be set as analog inputs. Note that if the PCR7~PCR0 bits are all set to zero, then all the PA7~PA0 pins will be setup as normal I/Os. ¸ C l o c k D i v i d e r N A C S R R e g i s t e r A D C A D R L A D R H A / D D a t a R e g i s t e r s A D C S 0 ~ A D C S 2 S T A R T E O C B A D C R R e g i s t e r C h a n n e l S e l e c t B i t s S t a r t B i t E n d o f C o n v e r s i o n B i t A D O N B B i t A / D E n a b l e f S Y S P A 0 / A N 0 P A 1 / A N 1 P A 6 / A N 6 P A 7 / A N 7 A/D Converter Structure |
类似零件编号 - HT56R22_14 |
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类似说明 - HT56R22_14 |
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