Tiêu đề JTAG (Int prep session 28 part 1).pdf ✅

JTAG +91-9986194191 | www.vlsiguru.com | www.inskill.in
+91-9986194191 | www.vlsiguru.com | www.inskill.in JOINT TEST ACTION GROUP (JTAG) [IEEE 1149.1 std] NEED OF JTAG : • To minimize the no. of ports from top level. • To achieve boundary scan.
+91-9986194191 | www.vlsiguru.com | www.inskill.in To minimize no. of ports from top level LIST OF SOME IMPORTANT SIGNALS : TM edt_bypass_en int_mode ext_mode int_ltest_en ext_ltest_en mbist_bypass_en These are just a list of important signals. There will be many more signals like these. If all these signals are to be controlled from top-level, then the no .of top level ports will increase drastically. So we use JTAG to internally control these signals. By using JTAG we need only 5 ports (TMS, TCLK, TRST, TDI, TDO) to control all the above signals.
+91-9986194191 | www.vlsiguru.com | www.inskill.in Using JTAG, we can control only static signals (signals that are constant throughout the run) Example : • edt_byass_en => static signal It will either be 0 or 1 for the complete run. It can be controlled using JTAG • edt_update => non static / dynamic signal For the same run, during load it will be 1, for the rest of the procedures it will be 0. This can’t be controlled using JTAG. We have to control from top level. • TM => static signal TM = 1 for the complete run It can be controlled using JTAG • SE => non static/ dynamic signal SE = 1 => during load and shift SE = 0 => during capture. It can’t be controlled using JTAG. We have to control it from top level.