Multi-purpose I/O
EBX-38 Hardware Reference Manual
33
P
OWER
S
TATES
CPU power states will affect voltage rails driving DIO circuits as described below:
The DIO power (which includes the pullup voltage) can be controlled (the same power
used for the 8x GPIOs on the CBR-4005 paddleboard) using an FPGA register setting.
By default, the DIOs power-down in sleep modes but can be configured to always stay
on (along with the GPIOs).
Power control during CPU power states on user devices connected to DIO lines is
dependent on the application design. These external devices would likely remain
powered unless a power-down mechanism is designed into the system.
Care must be taken when powered DIO signals are connected to un-powered DIO
signals. Significant voltage and current can be leaked from a powered system to an un-
powered system causing unpredictable results. Current limiting and/or diode isolation
can help.
C
ABLES
Cabling issues will affect the usable speed of DIO signals.
These are single-ended drivers/receivers.
Cabling crosstalk can be a problem with fast edge rates. The DIOs are slew-rate limited
and have 50
Ω
source terminators to minimize crosstalk and reflections.
A
NALOG
I/O
(AIO)
Analog Inputs
A Linear Tech LTC1857 A/D device operates off a single 5V supply to provide eight 12-bit
analog inputs. The LTC1857 provides eight single-ended input channels; or alternatively each
even and odd analog channel “pair” (for example inputs 1 and 2 or 5 and 6) can be combined as
differential inputs or you can also have combinations of both single-ended and differential
channels. The converter has a 100 kilo-samples-per-
second (ksps) sampling rate, with a 4 μs
acquisition time and per-channel input ranges of 0 to 5V, ±5V, 0 to +10V and ±10V.
Analog Outputs
A Linear Tech LTC2634 D/A device is used to provide four single-ended 12-bit outputs. The
converter has 5 μs per
-channel update rate with a 0 to 4.096V output voltage range.
The Analog Output interface connects to a CBR-2004 paddle board via the J32 I/O connector.
This is not considered a hot-plug interface and has no ESD protection.
