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SCAN921025 Dataheets PDF



Part Number SCAN921025
Manufacturers National Semiconductor
Logo National Semiconductor
Description 30-80 MHz 10 Bit Bus LVDS Serializer and Deserializer with IEEE 1149.1 (JTAG) and at-speed BIST
Datasheet SCAN921025 DatasheetSCAN921025 Datasheet (PDF)

SCAN921025/SCAN921226 30-80 MHz 10 Bit BLVDS Serializer and Deserializer with IEEE 1149.1 (JTAG) and at-speed BIST December 2001 SCAN921025 and SCAN921226 30-80 MHz 10 Bit Bus LVDS Serializer and Deserializer with IEEE 1149.1 (JTAG) and at-speed BIST General Description The SCAN921025 transforms a 10-bit wide parallel LVCMOS/LVTTL data bus into a single high speed Bus LVDS serial data stream with embedded clock. The SCAN921226 receives the Bus LVDS serial data stream and transforms it back int.

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SCAN921025/SCAN921226 30-80 MHz 10 Bit BLVDS Serializer and Deserializer with IEEE 1149.1 (JTAG) and at-speed BIST December 2001 SCAN921025 and SCAN921226 30-80 MHz 10 Bit Bus LVDS Serializer and Deserializer with IEEE 1149.1 (JTAG) and at-speed BIST General Description The SCAN921025 transforms a 10-bit wide parallel LVCMOS/LVTTL data bus into a single high speed Bus LVDS serial data stream with embedded clock. The SCAN921226 receives the Bus LVDS serial data stream and transforms it back into a 10-bit wide parallel data bus and recovers parallel clock. Both devices are compliant with IEEE 1149.1 Standard for Boundary Scan Test. IEEE 1149.1 features provide the design or test engineer access via a standard Test Access Port (TAP) to the backplane or cable interconnects and the ability to verify differential signal integrity. The pair of devices also features an at-speed BIST mode which allows the interconnects between the Serializer and Deserializer to be verified at-speed. The SCAN921025 transmits data over backplanes or cable. The single differential pair data path makes PCB design easier. In addition, the reduced cable, PCB trace count, and connector size tremendously reduce cost. Since one output transmits clock and data bits serially, it eliminates clock-todata and data-to-data skew. The powerdown pin saves power by reducing supply current when not using either device. Upon power up of the Serializer, you can choose to activate synchronization mode or allow the Deserializer to use the synchronization-to-random-data feature. By using the synchronization mode, the Deserializer will establish lock to a signal within specified lock times. In addition, the embedded clock guarantees a transition on the bus every 12-bit cycle. This eliminates transmission errors due to charged cable conditions. Furthermore, you may put the SCAN921025 output pins into TRI-STATE to achieve a high impedance state. The PLL can lock to frequencies between 30 MHz and 80 MHz. Features n IEEE 1149.1 (JTAG) Compliant and At-Speed BIST test mode. n Clock recovery from PLL lock to random data patterns. n Guaranteed transition every data transfer cycle n Chipset (Tx + Rx) power consumption < 600 mW (typ) @ 80 MHz n Single differential pair eliminates multi-channel skew n 800 Mbps serial Bus LVDS data rate (at 80 MHz clock) n 10-bit parallel interface for 1 byte data plus 2 control bits n Synchronization mode and LOCK indicator n Programmable edge trigger on clock n High impedance on receiver inputs when power is off n Bus LVDS serial output rated for 27Ω load n Small 49-lead BGA package Block Diagrams DS200248-1 © 2001 National Semiconductor Corporation DS200248 www.national.com SCAN921025/SCAN921226 Block Diagrams (Continued) Application DS200248-2 Functional Description The SCAN921025 and SCAN921226 are a 10-bit Serializer and Deserializer chipset designed to transmit data over differential backplanes at clock speeds from 30 to 80 MHz. The chipset is also capable of driving data over Unshielded Twisted Pair (UTP) cable. The chipset has three active states of operation: Initialization, Data Transfer, and Resynchronization; and two passive states: Powerdown and TRI-STATE. In addition to the active and passive states, there are also test modes for JTAG access and at-speed BIST. The following sections describe each operation and passive state and the test modes. The user’s application determines control of the SYNC1 and SYNC 2 pins. One recommendation is a direct feedback loop from the LOCK pin. Under all circumstances, the Serializer stops sending SYNC patterns after both SYNC inputs return low. When the Deserializer detects edge transitions at the Bus LVDS input, it will attempt to lock to the embedded clock information. When the Deserializer locks to the Bus LVDS clock, the LOCK output will go low. When LOCK is low, the Deserializer outputs represent incoming Bus LVDS data. Data Transfer After initialization, the Serializer will accept data from inputs DIN0–DIN9. The Serializer uses the TCLK input to latch incoming Data. The TCLK_R/F pin selects which edge the Serializer uses to strobe incoming data. TCLK_R/F high selects the rising edge for clocking data and low selects the falling edge. If either of the SYNC inputs is high for 5*TCLK cycles, the data at DIN0-DIN9 is ignored regardless of clock edge. After determining which clock edge to use, a start and stop bit, appended internally, frame the data bits in the register. The start bit is always high and the stop bit is always low. The start and stop bits function as the embedded clock bits in the serial stream. The Serializer transmits serialized data and clock bits (10+2 bits) from the serial data output (DO ± ) at 12 times the TCLK frequency. For example, if TCLK is 80 MHz, the serial rate is 80 x 12 = 960 Mega-bits-per-second. Since only 10 bits are from input data, the serial “payload” rate is 10 times the TCLK frequency. For instance, if TCLK = 80 MHz, the payload d.


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