BSCAN_VIRTEX

Virtex Boundary Scan Logic Control Circuit

The BSCAN_VIRTEX symbol is used to create internal boundary scan chains in a Virtex device. The 4-pin JTAG interface (TDI, TDO, TCK, and TMS) are dedicated pins in Virtex. To use normal JTAG for boundary scan purposes, just hook up the JTAG pins to the port and go. The pins on the BSCAN_VIRTEX symbol do not need to be connected, unless those special functions are needed to drive an internal scan chain.

A signal on the TDO1 input is passed to the external TDO output when the USER1 instruction is executed; the SEL1 output goes High to indicate that the USER1 instruction is active.The DRCK1 output provides USER1 access to the data register clock (generated by the TAP controller). The TDO2 and SEL2 pins perform a similar function for the USER2 instruction and the DRCK2 output provides USER2 access to the data register clock (generated by the TAP controller). The RESET, UPDATE, and SHIFT pins represent the decoding of the corresponding state of the boundary scan internal state machine. The TDI pin provides access to the TDI signal of the JTAG port in order to shift data into an internal scan chain.

Note: For specific information on boundary scan for an architecture, refer to The Programmable Logic Data Book.