Classification
Revision
Public
B
Document ID
Print date
20-2507
2022-03-31
7.4
Port Control
Some ports can be controlled from the second user logic area, using three signals per port pin:
•
The current value read from the pin.
•
Whether the pin is configured as an input (0) or an output (1), i.e. the pin’s
direction
.
•
The output value driven by the pin, if the pin is configured as an output.
An example of these signals for the TRIG port is shown below:
input wire ext_trig_i,
// Input value
output wire ext_trig_o,
// Output value
output wire ext_trig_direction_o,
// Direction
The input value for a pin is always accessible from the user logic area, while control of the output value
and the direction requires changing the pin’s
function
to
ADQ_FUNCTION_USER_LOGIC
. This is a configu-
ration parameter set from software, please refer to the
ADQ3 Series FWDAQ User Guide
] for more
information on how to change port functions.
Important
The port signals are
synchronous to the data clock
. While the enclosing design ensures that the input
signals are CDC synchronized, it also assumes that the output and direction signals are synchronous
to the data clock. The user must take care to fulfill this requirement.
7.4.1
Port Impedance
Some ports, e.g. TRIG, allow choosing between high impedance and low impedance input modes. To
enable the low impedance mode via the development kit, the direction must be set to
1
for output, and
the output value must be driven with a fixed
0
. This will effectively connect a low impedance termination
to ground in the pin’s signal path.
Note
Output impedance cannot be contolled by the user.
7.4.2
ADQ32-PCIe, ADQ33-PCIe
The ports on ADQ32-PCIe and ADQ33-PCIe that can be controlled from the second user logic area are:
•
TRIG, containing a single pin using single-ended signaling.
–
ext_trig_i
for the input value of pin 0.
–
ext_trig_o
for the output value of pin 0.
–
ext_trig_direction_o
for the direction of pin 0.
•
SYNC, containing a single pin using single-ended signaling.
–
ext_sync_i
for the input value of pin 0.
ADQ3 Series FWDAQ Development Kit
Page 33 of 38
