22
Virtex-6 FPGA System Monitor
UG370 (v1.1) June 14, 2010
Register File Interface
System Monitor JTAG DRP Read Operation
shows the timing for a SYSMON DR Read operation. The IR should contain the
DR-scan operation SYSMON instruction. A JTAG Read from the System Monitor DRP is a
two-step operation.
•
First, the SYSMON DR is loaded with the Read DRP instruction. This instruction is
transferred to the arbitrator during the Update-DR state and then the arbitrator reads
the selected DRP register and stores the newly read 16-bit data. This operation takes
several DCLK cycles to complete.
•
During the DR-Capture phase of the next DR-scan, newly read data is transferred
from the arbitrator to the SYSMON DR. This 16-bit data (stored in the 16 LSBs of the
32-bit word) is then shifted out on TDO during the subsequent shift operation (see
). The timing diagram shows a number of idle states at the end of the first
DR-scan operation, allowing the arbitrator enough time to fetch the System Monitor
DRP data.
As mentioned previously, if the DCLK frequency is significantly faster than the TCK, these
idle states might not be required.
Note:
Implementing a DR-scan operation before the arbitrator has completed the DRP-read
operation results in old DRP data being transferred to the SYSMON DR during the DR-capture
phase.
To ensure reliable operation over all operating clock frequencies, a minimum of ten Run-
Test-Idle (RTI) states should be inserted. Multiple Read operations can be pipelined, as
shown in
. Thus, as the result of a read operation is being shifted out of the
SYSMON DR, an instruction for the next read can be shifted in.
X-Ref Target - Figure 10
Figure 10:
System Monitor JTAG DRP Write Operation
TAP Controller States
TCK
TMS
TDI
TDO
0
9
0
31
30
MSB
MSB
MSB
MSB
LSB
LSB
LSB
LSB
Load IR with
SYSMON insructions
Idle between successive
Writes to allow DRP Write
operation to finish
Old DRP Write or New
Read Data shifted out
Write DRP Command shifted into
SYSMON DR
TLR TLR RTI
RTI
RTI
RTI
DRS
DRS
DRS
IRS CIR
CDR
CDR
SIR SIR SIR SIR
SDR SDR SDR
SDR SDR
EIR
EDR UDR
UIR
UG370_10_060809
www.BDTIC.com/XILINX