P4022 EM Microelectronic, P4022 Datasheet - Page 5

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

Timing Characteristics
1)
2)
3)
Anti-collision Protocol Overview
The protocols are a collection of simple but fast
and reliable anti-collision protocols. They allow
fast reading of large numbers of transponders
simultaneously using a single reader. It is even
possible to identify transponders with identical
codes, thereby making it
identical items.
Free-running protocol
The basis of the BTG-Supertag series of protocols
is that transponders transmit their own codes at
random times to a reader. By just listening and
recording unique codes when they are received,
the reader can eventually detect every tag. The
reader detects collisions by typically checking a
CRC. This basic protocol is known as the “Free-
running” protocol. It requires uniquely coded tags.
Its main advantage is that the reader design is
simple, and the spectrum requirement is much
less – a very narrow band is required.
Bi-directional protocols
Allowing bi-directional communication between
reader and transponders can speed up the basic
free-running protocol. Communication from the
reader to transponders is achieved by turning the
illuminating energy field off for short periods. The
transponders detect these gaps in the energy
transmission and interpret them as required.
Parameter
High frequency GAP width
High frequency ACK GAP width
High frequency MUTE and WAKE-UP GAP width
Low frequency ACK GAP width
Low frequency MUTE and WAKE-UP GAP width
GAP separation in WAKE-UP signal
All timings are derived from the on-chip oscillator, which can vary by 30%.
The minimum low frequency GAP width for a single chip is 1 bit at its own clock frequency. The reader
must however allow for the 30% spread in clock frequencies possible in a group of tags. Therefore the
minimum width of the GAP in MUTE and WAKE-UP signals must be 1.5 bits. High frequency GAPs can
be arbitrarily narrow (specified as minimum 50 ns).
The maximum GAP width for a single chip is 6 bits at its own clock frequency. The reader must
however allow for the 30% spread in clock frequencies possible in a group of tags. Therefore the
maximum width of the GAP in MUTE and WAKE-UP signals must be 5 bits.
EM MICROELECTRONIC-MARIN SA
possible to
count
T
T
T
T
T
Symbol Test conditions
HFGAP
HFGAP
HFGAP
LFGAP
LFGAP
Switch-off and Slow-down Modes
Reducing the effective population of transmitting
transponders in the reader field can speed up the
free-running protocol.
this is by either switching transponders off or
slowing them
detected. To achieve this, the reader sends an
ACK signal to a transponder after its code has
been successfully received. The transponder then
either switches off completely or reduces its
repeat rate until it is powered down. This reduces
the number of collisions between transponder
transmissions, thereby reducing the time required
to read a group of tags. The Switch-off protocol’s
main advantage is that identical transponders can
be counted.
In the P4022 the ACK signal is implemented as
two consecutive gaps with the appropriate timing
and received at a specific time after a code has
been transmitted.
Fast Mode
A second method of speeding up the reading of
tags,
transmitting while one transponder is transmitting.
This is done by sending a MUTE signal to all the
transponders when the start of a transmission is
detected.
enough to allow the transmission of one code.
This allows the transponder that has started
transmitting to complete its transmission without
any collisions. The other transponders continue
is
to
The transponders stay muted long
inhibit
down once
other
One method to achieve
Min
1.0
1.5
1.5
50
P4022
PRELIMINARY
transponders
they
Typ
have
Max Units
6
5
6
5
5
Table 6
been
from
ns
bit
bit
Bit
Bit
Bit
5