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XRT71D04 Datasheet(PDF) 19 Page - Exar Corporation |
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XRT71D04 Datasheet(HTML) 19 Page - Exar Corporation |
19 / 22 page ![]() áç áç áç áç XRT71D04 4 CHANNEL E3/DS3/STS-1 JITTER ATTENUATOR, STS-1 TO DS3 DESYNCHRONIZER REV. 1.1.1 18 3.0 MICROPROCESSOR SERIAL INTERFACE The serial interface for the XRT71D04 and the XRT73L00 family of E3/DS3/STS-1 LIU’s are the same, which makes it easy to configure both the XRT71D04 and the LIU with a single CS, SDI, SDO and SClk input and output pins. 3.1 SERIAL INTERFACE OPERATION. Serial interface data structure and timings are provid- ed in Figure 5 and 6 respectively. The clock signal is provided to the SClk and the CS is asserted for 50 ns prior to the first rising edge of the SClk. 3.1.1 Bit 1—R/W (Read/Write) Bit This bit will be clocked into the SDI input, on the first rising edge of SClk (after CS has been asserted). This bit indicates whether the current operation is a Read or Write operation. A “1” in this bit specifies a Read operation; whereas, a “0” in this bit specifies a Write operation. 3.1.2 Bits 2 through 6—A0, A1, A2 ,A3, and A4 The five (5) bit Address Values. The next five rising edges of the SClk signal will clock in the 5-bit address value for this particular Read (or Write) operation. The address selects the Command Register for reading data from, or writing data to. The address bits to the SDI input pin is applied in ascend- ing order with the LSB (least significant bit) first. 3.1.3 Bit 7—A5 A5 must be set to “0”, as shown in Figure 9. 3.1.4 Bit 8—A6 The value of A6 is a don’t care. Once these first 8 bits have been written into the Seri- al Interface, the subsequent action depends upon whether the current operation is a Read or Write op- eration. 3.1.5 Read Operation Once the last address bit (A4) has been clocked into the SDI input, the Read operation will proceed through an idle period, lasting three SClk periods. On the falling edge of SClk Cycle #8 (see Figure 9) the serial data output signal (SDO) becomes active. At this point the user can begin reading the data con- tents of the addressed Command Register (at Ad- dress [A4,A3, A2, A1, A0]) via the SDO output pin. The Serial Interface will output this eight bit data word (D0 through D7) in ascending order (with the LSB first), on the falling edges of the SClk . The data (on the SDO output pin) is stable for reading on the very next rising edge of the SClk . 3.1.6 Write Operation Once the last address bit (A4) has been clocked into the SDI input, the Write operation will proceed through an idle period, lasting three SClk periods. Pri- or to the rising edge of SClk Cycle #9 , the eight bit data word is applied to SDI input. Data on SDI is latched on the rising edge of SClk. TABLE 4: ADDRESS AND BIT FORMATS OF THE COMMAND REGISTERS ADDR COMMAND REGISTER TYPE D7 D6 D5 D4 D3 D2 D1 D0 0X06 CR6 R/W *** *** STS-1_0 DS3/E3_0 DJA_0 RRClkES_0 RClkES_0 FSS_0 0x07 CR7 RO *** *** *** *** *** *** *** FL_0 0x0E CR14 R/W *** *** STS-1_1 DS3/E3_1 DJA_1 RRClkES_1 RClkES_1 FSS_1 0x0F CR15 RO *** *** *** *** *** *** *** FL_1 0x16 CR22 R/W *** *** STS-1_2 DS3/E3_2 DJA_2 RRClkES_2 RClkES_2 FSS_2 0x17 CR23 RO *** *** *** *** *** *** *** FL_2 0x1E CR30 R/W *** *** STS-1_3 DS3/E3_3 DJA_3 RRClkES_3 RCLKES_3 FSS_3 0x1F CR31 RO *** *** *** *** *** *** *** FL_3 |