Your satalite decoder will most probably have one too, although they are taking them out now for security issues. gtyler ----- Original Message ----- From: "Barry Gershenfeld" To: Sent: Wednesday, June 04, 2003 9:45 PM Subject: Re: [PIC]: JTAG > >Sounds interesting, would you happen to know where I could see a simple > example of a JTAG circuit application or any part numbers of IC's using JTAG > so that I can look up the data sheet. > >Thanks, > >Tim > > >JTAG = Joint Test Action Group. It is a defined five pin hardware and > >serial communication protocol to primarily allow JTAG equipped complex IC's > >to be daisy chained together and functionaly tested in circuit. It is also > >used as a programming protocol for some devices. > >Regards > >Mike > > JTAG is a lot like SPI. In fact, it has the same reset-clock-data-in/out > connections. The one I saw ran at 10 MHz. There may be some kind > of command/data protocol but I think most of the protocol > is specific to the JTAG hardware inside each processor. > > It can be used to read out the state of each pin, some or all > registers, and anything else the manufacturer/designer saw > fit to connect it to. Likewise you can write to these things > to pre set them. The way JTAG can load a program is by using > memory write cycles to place a program in memory...usually a > loader program. > > ARM processors have it. So did the Pentium II (but not the AMD). > Probably later Pentium chips but I don't know. > > Barry > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body