User's Manual

8
Micro-reader - Reference Guide May ’00
1.2.4 Trigger Mode
When the Micro-reader is in idle mode it is possible to trigger a single charge-only
read with a power burst duration of 50 ms by taking the RDEN- pin to logic high for
100 µs. The single read will start on the falling edge of the 100 µs pulse.
If a transponder command is sent to the Micro-reader via the SCI while RDEN- is in
a logic high state (waiting position), a falling edge would trigger execution of the com-
mand. In waiting position the Micro-reader can only store one command. This means
that if two commands were to be sent to the Micro-reader while it is in the waiting po-
sition the second command will overwrite the first one.
1.2.5 Continuous Mode
When the CRDM input is active the Micro-reader goes into continuous charge-only
read mode using a power burst duration of 50 ms. The serial data input takes priority
over the CRDM input such that if a serial command is received it will be executed
regardless of the state of the CRDM input. After the execution of the serial data com-
mand the Micro-reader continues with the previous read mode.
In the default continuous read mode, only those valid RO, R/W or MPT IDs that differ
from the previously read ID; or valid IDs read after a “NO READ”, are transferred via
the SCI (Normal Mode). The Micro-reader can be set to transfer all valid IDs that are
read (Line Mode) by means of a corresponding serial data command.
Without synchronization the Micro-reader has a reading frequency of approximately
10 readouts per second using a power burst duration of 50 ms. Timing is given in
more detail in section 3.2.
1.2.6 Serial Communication
The two serial I/O pins are configured for 9600 Baud, 1 start bit, 8 data bits, no parity
and 1 stop bit; they can be connected directly to a communications driver to allow a
half duplex communication with a PC via its serial communications interface (for ex-
ample: RS232 or RS422).
The communications protocol is specified in Chapter 2.
Handshake
The Micro-reader accepts handshake commands X
on
/X
off
. When it receives an X
off
(13
hex
) the Micro-reader stops its current operation and stops transmitting data via
the serial port. It stays in idle mode until X
on
(11
hex
) is received when it continues with
the previous mode/command. During this idle period the Micro-reader accepts com-
mands via the serial port, however, it waits for its execution until X
on
is received. In
this idle period the Micro-reader can store only one command.
Note:
It is not recommended to have both wired and wireless synchroniza-
tion switched on as synchronization could be unreliable.
We recommend the use of bus drivers for wired synchronization with
other Micro-readers and to prevent ESD damage.
Wired or wireless synchronization prolongs the cycle time by typically
20 ms.