BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
436
Section 15: JTAG and Debug
Document
1250_1125-UM100CB-R
Figure 88: Example JTAG Probe Flowchart
An external debugger connected to the JTAG probe can use both master and slave accesses to communicate
with the part. An example flow is shown in
. Normally the debugger will scan out the Control Register
and service CPU requests. When it needs to run an access (for example to read memory) it will scan in the
Control Register with the MaSl bit set. A check needs to be done for CPU accesses that may have arrived while
the mode was being changed, once they are serviced the interface is ready for the master access.
Need JTAG
Scan Out
Scan In/Out
to ZBbus?
EJTAG Control Register
PrAcc Bit = 1?
Service
CPU Access
Y
N
N
Y
PrAcc Bit = 1?
Service
CPU Access
Run JTAG
Bus Cycle
EJTAG Control Register
With MaSl = 1
Scan Out
EJTAG Control Register
PrAcc Bit = 1
N
Y
N
Y
More JTAG
Cycles Needed?
Scan In/Out
EJTAG Control Register
with MaSl=0
N
Y