|JTAGer is a Windows 2K/ME/XP application that interfaces
two BST chains from a PC parallel port. This application was developed by
a (former) student called Tiago José Espinha de Mendonça Gasiba, as part of the 2001 / 02 edition
of a design for test course delivered at FEUP. The JTAGer entry on the
menu (left) provides instructions for downloading and installing this
JTAGer's main window looks as illustrated in figure 1
below. When first launched, the program should produce a blank file and a
"Driver successfully started" status message. The small
squares on the left of each code line enable the user to suspend test program
execution by inserting breakpoints, as shown below for code line 5.
Fig. 1: JTAGer start up window.
JTAGer provides the following alternatives to support hands-on sessions
with 1149.1 boards (containing one or two BS chains):
- Test program execution from the main JTAGer window: The sequence of test actions may be coded into a test program file,
using a low-level assembly-like language compatible with the BS test
controller model that was presented in the previous chapter. JTAGer
provides four execution modes for this test program, as follows:
decomposes each instruction into the corresponding elementary test
action and executes them one by one.
- Step-by-Step executes one
instruction at a time.
- Execute runs the whole test program, stopping when a breakpoint is found, a "halt"
instruction is found, or a Run: Pause command is issued. Test
program execution in this mode takes place under control of a
timer that launches a new event every millisecond (each
instruction corresponds to a specific number of events, meaning
that test program execution rate will never exceed a few hundred
instructions per second in this mode)
- Speed Run provides the fastest execution method, since a new
instruction is launched as soon as possible (depending only on CPU
performance). However, and since JTAGer does not respond to menu
or control bar commands in this mode, the program will lock if a cycle is found.
- Interactive interface with the two TAPs through an utility called
Bitstream shifter: Specific bit streams may be shifted in directly while the
corresponding output bit streams are displayed. This mode supports
direct interaction with the BS chains, and does not require a previous
specification of the sequence of test actions (in the form of a test
program) that will be carried out.
- Direct access to the TAP pins through an utility called Parallel
Port: Low-level test actions, such as setting TMS to 1, applying a single
pulse in TCK, etc., may also be carried out, if required for debugging
or demonstration purposes.
Each of these operating modes will be described ahead in further detail, following
the presentation of the set up information for this application.