Spectrum Brands Quad C6x VME64 - Manual (Page 49)

Spectrum Signal Processing Monaco Technical Reference
JTAG Debugging
Part Number 500-00191 37
Revision 2.00
7 JTAG Debugging
The Monaco board supports JTAG in-circuit emulation from a built in 74ACT8990 Test
Bus Controller. The 74ACT8990 Test Bus Controller permits the VME interface to
operate the JTAG chain. There are also two JTAG connectors for an XDS510 or White
Mountain debugger, JTAG IN (J1) and JTAG OUT (J2), which can route the JTAG
chain off-board.
JTAG in-circuit emulation is fed to the Test Bus Controller from the VME A24
secondary interface. C source debugging using an emulator board running a debug
monitor on an adjacent computer is supported through the JTAG IN connector. If a
JTAG IN connection with a clock signal is present the Test Bus Controller is
automatically disconnected.
JTAG data lines are routed to each available ‘C6x node. The full JTAG chain is shown
in the following diagram. Unpopulated processor nodes are bypassed.
The JTAG IN input is buffered to reduce the load on an external JTAG device. The
JTAG OUT output is buffered to guarantee enough drive to external JTAG loads. Up to
three Monaco boards can be chained together through JTAG.
Node D
‘C6x
TDO
TDI
JTAG IN or TBC
Node C
‘C6x
JTAG OUT
TDO
TDI
TDO
TDO
Node B
‘C6x
TDI
Node A
‘C6x
TDI
The Test Bus Controller
(TBC) is disabled
(bypassed) if an external
debugger is connected to
the JTAG IN connector.
TDO
TDO
TDI
Routed back
to JTAG IN if
nothing is
connected to
JTAG OUT
Figure 11 JTAG Chain