Emulation Design Considerations
15-23
Designing for JTAG Emulation
15.9.4 Performing Diagnostic Applications
For systems that require built-in diagnostics, it is possible to connect the
emulation scan path directly to a TI ACT8990 test bus controller (TBC) instead
of the emulation header. The TBC is described in the Texas Instruments
Ad-
vanced Logic and Bus Interface Logic Data Book (literature number
SCYD001). Figure 15–13 shows the scan path connections of
n devices to the
TBC.
Figure 15–13. TBC Emulation Connections for n JTAG Scan Paths
JTAG0
JTAGN
TDI
EMU1
TMS
TDO
EMU0
TRST
TCK
TDO
TCK
TRST
EMU1
EMU0
TMS
TDI
Clock
TDI1
TDI0
TCKO
TMS5/EVNT3
TMS4/EVNT2
TMS3/EVNT1
TMS2/EVNT0
TMS1
TMS0
TDO
TCKI
VCC
TBC
In the system design shown in Figure 1–13, the TBC emulation signals TCKI,
TDO, TMS0, TMS2/EVNT0, TMS3/EVNT1, TMS5/EVNT3, TCKO, and TDI0
are used, and TMS1, TMS4/EVNT2, and TDI1 are not connected. The target
devices’ EMU0 and EMU1 signals are connected to V
CC
through pullup resis-
tors and tied to the TBC’s TMS2/EVNT0 and TMS3/EVNT1 pins, respectively.
The TBC’s TCKI pin is connected to a clock generator. The TCK signal for the
main JTAG scan path is driven by the TBC’s TCKO pin.