Matrix E-blocks Notice D'utilisation page 7

Sharing a port
There are times when you need to split a
port into several sections, or where signals
on a port need to be shared between two or
more downstream E-blocks boards. In this
case you need to use a splitter cable. As an
example of this: supposing that you wanted to
develop a system that used two external ana-
logue sensors. The Sensor board only has the
capability for one external analogue sensor, so
you need to use a splitter cable and the patch
system to make the appropriate connections.
The resulting system would look something
like the one shown in Figure 15.
The splitter cable allows you to connect one
upstream port to two downstream ports us-
ing IDC (Insulation Displacement Connector)
connectors and ribbon cable. Here the link
blocks on both boards are in the 'patch' posi-
tion. On the top board the Analogue sensor
is routed to bit 1, and on the bottom board
the Analogue sensor is routed to bit 2. This
technique allows you share ports between
several devices - this is particularly convenient
for communications systems where a device's
serial port has to be shared.
Protecting E-blocks circuitry
Where possible leaded components have
been used for all devices on E-blocks boards
that can be subjected to electrical damage.
This means that in the case where devices on
the E-blocks boards do become damaged, the
task of replacing them is very simple.
Some upstream boards (ARM processor
boards and FPGA board) make use of surface
mounted technology components which can
not be socketed and which are not easy to
solder. In these cases we have used smaller
Fig 15 - Two sensor boards and a splitter cable
daughter board so that if the key device is
broken then you can simply order a new
daughter board.
To protect upstream components, all down-
stream E-blocks have been developed with
protective resistors so that it is not possible
to damage an upstream E-block by improperly
declaring an input as an output, and having
two output pins with different output levels
clash.
However there are circumstances where it
will still be possible to electrically damage
your E-blocks:
• When using screw terminal connectors turn
power off when routing power wires.
• When connecting two upstream boards
together with a gender changer or IDC
cable then you are connecting one output to
another. It is strongly recommended that you
use protective resistors for the lines you
need to connect to prevent chip damage.
• Although modern chips are less prone to
static damage these days, you are advised to
make sure you are earthed before handling
E-blocks circuit boards. If you have not got
access to an antistatic wristband then quickly
touching a radiator or other earthed device
will minimise the likelihood of static damage.
• When using a patch or prototype board you
have the opportunity to connect external
components directly to the pin of the micro
controller or CPLD device. This also means
that you have the opportunity to short
circuit the device to 0V or +V.
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