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SN74ABTH18646APM Datasheet(PDF) 11 Page - Texas Instruments |
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SN74ABTH18646APM Datasheet(HTML) 11 Page - Texas Instruments |
11 / 37 page SN54ABTH18646A, SN54ABTH182646A, SN74ABTH18646A, SN74ABTH182646A SCAN TEST DEVICES WITH 18-BIT TRANSCEIVERS AND REGISTERS SCBS166D – AUGUST 1993 – REVISED JULY 1996 11 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 data register description boundary-scan register The boundary-scan register (BSR) is 52 bits long. It contains one boundary-scan cell (BSC) for each normal-function input pin, one BSC for each normal-function I/O pin (one single cell for both input data and output data), and one BSC for each of the internally decoded output-enable signals (1OEA, 2OEA, 1OEB, 2OEB). The BSR is used 1) to store test data that is to be applied externally to the device output pins, and/or 2) to capture data that appears internally at the outputs of the normal on-chip logic and/or externally at the device input pins. The source of data to be captured into the BSR during Capture-DR is determined by the current instruction. The contents of the BSR can change during Run-Test/Idle as determined by the current instruction. At power up or in Test-Logic-Reset, BSCs 51–48 are reset to logic 0, ensuring that these cells, which control A-port and B-port outputs, are set to benign values (i.e., if test mode were invoked, the outputs would be at high-impedance state). Reset values of other BSCs should be considered indeterminate. When external data is to be captured, the BSCs for signals 1OEA, 2OEA, 1OEB, and 2OEB capture logic values determined by the following positive-logic equations: 1OEA = 1OE • 1DIR, 2OEA = 2OE • 2DIR, 1OEB = 1OE • DIR, and 2OEB = 2OE • DIR. When data is to be applied externally, these BSCs control the drive state (active or high impedance) of their respective outputs. The BSR order of scan is from TDI through bits 51–0 to TDO. Table 1 shows the BSR bits and their associated device pin signals. Table 1. Boundary-Scan Register Configuration BSR BIT NUMBER DEVICE SIGNAL BSR BIT NUMBER DEVICE SIGNAL BSR BIT NUMBER DEVICE SIGNAL 51 2OEB 35 2A9-I/O 17 2B9-I/O 50 1OEB 34 2A8-I/O 16 2B8-I/O 49 2OEA 33 2A7-I/O 15 2B7-I/O 48 1OEA 32 2A6-I/O 14 2B6-I/O 47 2DIR 31 2A5-I/O 13 2B5-I/O 46 1DIR 30 2A4-I/O 12 2B4-I/O 45 2OE 29 2A3-I/O 11 2B3-I/O 44 1OE 28 2A2-I/O 10 2B2-I/O 43 2CLKAB 27 2A1-I/O 9 2B1-I/O 42 1CLKAB 26 1A9-I/O 8 1B9-I/O 41 2CLKBA 25 1A8-I/O 7 1B8-I/O 40 1CLKBA 24 1A7-I/O 6 1B7-I/O 39 2SAB 23 1A6-I/O 5 1B6-I/O 38 1SAB 22 1A5-I/O 4 1B5-I/O 37 2SBA 21 1A4-I/O 3 1B4-I/O 36 1SBA 20 1A3-I/O 2 1B3-I/O 19 1A2-I/O 1 1B2-I/O 18 1A1-I/O 0 1B1-I/O |
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