Technical data

Capturing port driver data with -dumpports
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Value Change Dump (VCD) Files ModelSim EE/PLUS Reference Manual
Capturing port driver data with -dumpports
Some ASIC vendor’s toolkits read a VCD file format that provides details on
port’s drivers. This information can be used, for example, to drive a tester. See the
ASIC vendor’s documentation for toolkit specific information.
Execute the
vcd file
command (p382) with the
-dumpports
option to specify that
you are capturing port driver data. Follow the
vcd file
command by
vcd add
commands (p379) on the ports you wish to capture.
Port driver direction information is captured as TSSI states in the VCD file. Each
time an external or internal port driver changes values, a new value change is
recorded in the VCD file with the following format:
p<TSSI state> <0 strength> <1 strength> <identifier_code>
Supported TSSI states
The supported <TSSI states> are:
Input (testfixture) Unknown direction
D low 0 low (both input and output are driving low)
U high 1 high (both input and output are driving high)
N unknown ? unknown (both input and output are driving unknown)
Z tri-state f tri-state
A unknown (input driving low and output driving high)
Output (dut)
a unknown (input driving low and output driving unknown)
L low C unknown (input driving unknown and output driving low)
H high b unknown (input driving high and output driving unknown)
X unknown B unknown (input driving high and output driving low)
T tri-state c unknown (input driving unknown and output driving high)