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AD9544/PCBZ 数据表(PDF) 57 Page - Analog Devices |
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AD9544/PCBZ 数据表(HTML) 57 Page - Analog Devices |
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57 / 62 page ![]() Data Sheet AD9544 Rev. 0 | Page 57 of 62 autoclearing bit). The other is to use an external signal via an appropriately programmed multifunction pin. The user can change as many register bits as desired before executing an input/output update. The input/output update operation transfers the buffer register contents to their active register counterparts. Read If the instruction word indicates a read operation, the next N × 8 SCLK cycles clock out the data starting from the address specified in the instruction word, where N is the number of data bytes to read. Read data appears on the appropriate data pin (SDIO or SDO) on the falling edge of SCLK. The user must latch the read data on the rising edge of SCLK. Note that the internal SPI control logic does not skip over blank registers during a readback operation. A readback operation takes data from either the serial control port buffer registers or the active registers, as determined by Register 0x01, Bit 5. SPI Instruction Word (16 Bits) The MSB of the 16-bit instruction word is R/W, which indicates whether the ensuing operation is read or write. The next 15 bits are the register address (A14 to A0), which indicates the starting register address of the read/write operation (see Table 35). Note that SPI controller ignores A14, treating it as Logic 0, because the AD9544 has no register addresses requiring more than a 14-bit address word. SPI MSB-/LSB-First Transfers The AD9544 instruction word and payload can be transferred MSB first or LSB first. The default for the AD9544 is MSB first. To invoke LSB first mode, write a Logic 1 to Register 0x00, Bit 6. Immediately after invoking LSB first mode, subsequent serial control port operations are LSB first. Address Ascension If the address ascension bit (Register 0x0000, Bit 5) is Logic 0, serial control port register addressing decrements from the specified starting address toward Address 0x0000. If the address ascension bit (Register 0x0000, Bit 5) is Logic 1, serial control port register addressing increments from the starting address toward Address 0x3A3B. Reserved addresses are not skipped during multibyte input/output operations; therefore, write the default value to a reserved register and Logic 0s to unmapped registers. Note that it is more efficient to issue a new write command than to write the default value to more than two consecutive reserved (or unmapped) registers. Table 34. Streaming Mode (No Addresses Skipped) Address Ascension Stop Sequence Increment 0x0000 … 0x3A3B Decrement 0x3A3B … 0x0000 Table 35. Serial Control Port, 16-Bit Instruction Word MSB LSB I15 I14 I13 I12 I11 I10 I9 I8 I7 I6 I5 I4 I3 I2 I1 I0 R/W A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 CSB SCLK DON'T CARE SDIO A12 A13 A14 R/W A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 DON'T CARE DON'T CARE DON'T CARE 16-BIT INSTRUCTION HEADER REGISTER (N) DATA REGISTER (N – 1) DATA Figure 53. Serial Control Port Write—MSB First, Address Decrement, Two Bytes of Data CSB SCLK SDIO SDO REGISTER (N) DATA 16-BIT INSTRUCTION HEADER REGISTER (N – 1) DATA REGISTER (N – 2) DATA REGISTER (N – 3) DATA A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 DON'T CARE DON'T CARE DON'T CARE DON'T CARE D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 Figure 54. Serial Control Port Read—MSB First, Address Decrement, Four Bytes of Data tS DON'T CARE DON'T CARE A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 D4 D3 D2 D1 D0 DON'T CARE DON'T CARE R/W tDS tDH tHIGH tLOW tCLK tC CSB SCLK SDIO Figure 55. Timing Diagram for Serial Control Port Write—MSB First |
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