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ISL22416UFU10Z Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL22416UFU10Z Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 14 page 10 FN6227.2 September 9, 2009 Bus Interface Pins SERIAL CLOCK (SCK) This is the serial clock input of the SPI serial interface. SERIAL DATA OUTPUT (SDO) The SDO is an open drain serial data output pin. During a read cycle, the data bits are shifted out at the falling edge of the serial clock SCK, while the CS input is low. SDO requires an external pull-up resistor for proper operation. SERIAL DATA INPUT (SDI) The SDI is the serial data input pin for the SPI interface. It receives device address, operation code, wiper address and data from the SPI external host device. The data bits are shifted in at the rising edge of the serial clock SCK, while the CS input is low. CHIP SELECT (CS) CS LOW enables the ISL22416, placing it in the active power mode. A HIGH to LOW transition on CS is required prior to the start of any operation after power up. When CS is HIGH, the ISL22416 is deselected and the SDO pin is at high impedance, and (unless an internal write cycle is underway) the device will be in the standby state. Principles of Operation The ISL22416 is an integrated circuit incorporating one DCP with its associated registers, non-volatile memory and the SPI serial interface providing direct communication between host and potentiometer and memory. The resistor array is comprised of individual resistors connected in series. At either end of the array and between each resistor is an electronic switch that transfers the potential at that point to the wiper. The electronic switches on the device operate in a “make before break” mode when the wiper changes tap positions. When the device is powered down, the last value stored in IVR will be maintained in the non-volatile memory. When power is restored, the contents of the IVR is recalled and loaded into the WR to set the wiper to the initial value. DCP Description The DCP is implemented with a combination of resistor elements and CMOS switches. The physical ends of each DCP are equivalent to the fixed terminals of a mechanical potentiometer (RH and RL pins). The RW pin of the DCP is connected to intermediate nodes, and is equivalent to the wiper terminal of a mechanical potentiometer. The position of the wiper terminal within the DCP is controlled by a 7-bit volatile Wiper Register (WR). When the WR of a DCP contains all zeroes (WR<6:0>: 00h), its wiper terminal (RW) is closest to its “Low” terminal (RL). When the WR register of a DCP contains all ones (WR<6:0>: 7Fh), its wiper terminal (RW) is closest to its “High” terminal (RH). As the value of the WR increases from all zeroes (0) to all ones (127 decimal), the wiper moves monotonically from the position closest to RL to the closest to RH. At the same time, the resistance between RW and RL increases monotonically, while the resistance between RH and RW decreases monotonically. While the ISL22416 is being powered up, the WR is reset to 40h (64 decimal), which locates RW roughly at the center between RL and RH. After the power supply voltage becomes large enough for reliable non-volatile memory reading, the WR will be reload with the value stored in a non-volatile Initial Value Register (IVR). The WR and IVR can be read or written to directly using the SPI serial interface as described in the following sections. Memory Description The ISL22416 contains one non-volatile 7-bit register, known as the Initial Value Register (IVR), volatile 7-bit Wiper Register (WR), and volatile 8-bit Access Control Register (ACR). The memory map is shown in Table 1. The non-volatile register (IVR) at address 0, contain initial wiper position and volatile registers (WR) contain current wiper position. The non-volatile IVR and volatile WR registers are accessible with the same address. The Access Control Register (ACR) contains information and control bits described in Table 2. The VOL bit (ACR<7>) determines whether the access is to wiper registers WR or initial value registers IVR. If VOL bit is 0, the non-volatile IVR register is accessible. If VOL bit is 1, only the volatile WR is accessible. Note, value is written to IVR register also is written to the WR. The default value of this bit is 0. The SHDN bit (ACR<6>) disables or enables Shutdown mode. This bit is logically ANDed with SHDN pin. When this bit is 0, DCP is in Shutdown mode. Default value of SHDN bit is 1. The WIP bit (ACR<5>) is read only bit. It indicates that non-volatile write operation is in progress. The WIP bit can be read repeatedly after a non-volatile write to determine if the write has been completed. It is impossible to write to the WR or ACR while WIP bit is 1. TABLE 1. MEMORY MAP ADDRESS NON-VOLATILE VOLATILE 2— ACR 1Reserved 0IVR WR TABLE 2. ACCESS CONTROL REGISTER (ACR) BIT # 76 5 432 1 0 BIT NAME VOL SHDN WIP 000 0 0 ISL22416 |
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