P4022 EM Microelectronic, P4022 Datasheet - Page 6

• Manufacturer Part Number: P4022
• Description: Multi Frequency Contactless Identification Device
• Manufacturer: EM Microelectronic

with their own protocols automatically after a time
out, or continue immediately upon detection of
an ACK signal indicating that the transmission
which caused the MUTE has been completed.
In the P4022 the MUTE signal is implemented as
a single gap received while the transponder is not
transmitting.
Protocol combinations
The FREE-RUNNING and the two basic bi-
directional protocols, SWITCH-OFF and SLOW-
DOWN, can all be combined with the Fast
protocol to give six different protocols, i.e. Normal
FREE-RUNNING, Normal SLOW-DOWN, Normal
SWITCH-OFF,
DOWN, and Fast SWITCH-OFF.
The following should be noted about the different
protocols:
1) The SWITCH-OFF protocols must be used for
2) All the protocols except the SWITCH-OFF
3) Normal FREE-RUNNING is the only
4) Fast SWITCH-OFF and Fast SLOW-DOWN are
5) For 125 kHz inductive applications using a 4
6) For RF applications using a 64 kbit/s data rate,
Reader determined protocols
If the reader does not send MUTE signals to
transponders that were programmed for one of the
FAST protocols, the protocol merely reverts to the
equivalent normal protocol. Similarly,
reader does not send ACK signals to transponders
that were programmed
SWITCH-OFF, the protocol reverts to a FREE-
RUNNING protocol.
can determine the protocol that is used.
counting applications.
protocols have built in redundancy because of
the fact that they can transmit a code more
than once.
directional protocol. It has the lowest power
spectrum requirement because the reader
transmits a CW wave.
the fastest protocols, and should be used
where speed is important, or where the data
rate limits the reading rate. Fast SLOW-DOWN
is slightly slower, but theoretically has a lower
error rate.
kbit/s data rate, Fast SLOW-DOWN is probably
the best overall protocol.
normal FREE-RUNNING protocol is probably
the best protocol.
Fast
EM MICROELECTRONIC-MARIN SA
In this manner, the reader
FREE-RUNNING,
for
SLOW-DOWN
SLOW-
if
uni-
the
or
Note, however, that unless a transponder was
specifically programmed for the FREE-RUNNING
protocol, its GAP input must be pulled down. This
happens automatically in low frequency inductive
applications, where the GAP input is pulled down
by the internal GAP detector diode.
applications, however, the GAP input will have to
be pulled down explicitly.
extra current.
Protocol saturation
As the number of transponders in a reader beam is
increased, the number of collisions increase, and
it takes longer to read all the tags. This process is
not linear. To read twice as many transponders
could take more than twice as long. This effect is
called protocol saturation.
The normal FREE-RUNNING protocol saturates
the easiest of all the protocols, because it does
not have any means of reducing the transmitting
population.
hand, are virtually immune against saturation, as
they prevent collisions by muting all transponders
except the transmitting one.
One way of delaying the onset of saturation, is to
reduce the initial repeat rate (not data rate) at
which transponders transmit their codes. This is
done by increasing the maximum random delay
between transmissions.
are available from 16 bits to 64 kbits. A higher
setting means it will take longer to read a small
number of tags, but it will take a larger number of
transponders
channel.
Table 7 below compares reading times at 4 kbit/s
vs. the number of transponders in a group.
each case the repeat delay was optimised for a
group of 30 transponders.
No of transponders
Free-running
Slow-down
Switch-off
Fast Free-running
Fast Slow-down
Fast Switch-off
The Fast protocols, on the other
to
saturate
0.86
0.79
0.30
0.27
0.26
3.1
3
Seven different settings
0.78
0.55
0.49
5.8
1.8
1.5
10
the
P4022
PRELIMINARY
This will consume
Time (s)
10.8
communication
5.8
3.4
2.9
1.4
1.0
30
49.3
100
6.2
3.3
89
34
21
Table 7
In RF
300
690
33
13
In
6
-
-
-