PSCAN-D-1D-D2 Division 2 Barcode Reader
70
Subject to modifications
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REFERENCES
161
5.1.2 ACK/NACK Protocol
PowerScan
®
D8330 Readers
This parameter sets a transmission protocol in which the Host responds to the reader
after every code transmitted. The Host sends an ACK character (06 HEX) in the case
of good reception or the NACK character (15 HEX) requesting re-transmission, in the
case of bad reception.
PowerScan
®
D8330
Host
ACK or NACK
data
cable
ACK/NACK enabled
If the reader does not receive an ACK or NACK, transmission is ended after the
RX Timeout (see par. 5.1.4).
When ACK/NACK protocol is enabled, FIFO must be disabled manually, see par.
5.1.3.
PowerScan
®
M8300 Readers
The transmission protocol takes place between reader, cradle and Host. The reader
passes its data (code read) to the cradle, which sends it to the Host. The
management of responses (from Host or cradle) depends on the Transmission Mode
parameter, see par. 5.9.4.
In the following descriptions the completed transmission is indicated by the Beeper
Control for Radio Response parameter with its default setting to Normal, see par.
5.9.5.
When ACK/NACK is disabled (in One-Way tx mode), there is no control from cradle
to Host transmission, the reader responds with the good reception tone.
BC-80X0
Host
data
cable
PowerScan
®
M8300
data
Transmission Mode = One-Way
good RX
beep
ACK/NACK disabled
References
ACK/NACK protocol
PSCAN-D-1D-D2 readers
This parameter sets a transmission protocol in which the host
responds to the reader after every code transmitted. The host sends
an ACK character (06 HEX) in the case of good reception or the NACK
character (15 HEX) requesting re-transmission, in the case of bad
reception
If the reader does not receive an ACK or NACK, transmission is ended
after the RX Timeout. When ACK/NACK protocol is enabled, FIFO must
be disabled manually.
FIFO
PSCAN-D-1D-D2 readers
This parameter determines whether data (barcodes) are buffered
on a First In First Out basis allowing faster data collection in certain
cases, for example when using slow baud rates and/or hardware
handshaking. If the FIFO buffering is enabled, codes are collected
and sent out on the serial line in the order of acquisition. About
800 characters can be collected (buffer full), after which the reader
signals an error and discards any further codes until the transmission
is restored. If the FIFO buffering is disabled, each code must be
transmitted before another one can be read.
RX timeout
When the RS-232 interface is selected, the host can be used to
configure the device by sending it command strings. This parameter
can be used to automatically end data reception from the host after
the specified period of time. If no character is received from the
host, after the timeout expires, any incomplete string (any string not
terminated by <CR>) is flushed from the device buffer.
Reading parameters
Trigger signal
This mode determines how the reading phase is controlled when the
hardware trigger operating mode is selected:
•
Trigger active level:
the reader goes ON when the trigger is
pressed and goes OFF when it is released
•
Trigger active pulse:
the reader goes ON at the first trigger press
and goes OFF only at a second press
Trigger click
When enabled, it activates a "click" sound upon each trigger pressure.
Trigger-off timeout
When this timeout is selected, the reader turns OFF automatically after
the desired period of time.
Reads per cycle
In general, a reading cycle corresponds to the ON + OFF times of a device.
The resulting effects of this parameter on code reading depend on other
related configuration conditions. Here are the definitions of ON and OFF
times.
•
For readers using the software trigger parameter (FLASH MODE), a
reading cycle corresponds to the flash on + flash off times. Code
reading takes place during the flash on time.
•
For readers using the hardware trigger parameter, a reading cycle
corresponds to a trigger press (ON) + one of the following OFF
events: trigger release (for trigger active level) a second trigger press
(for trigger active pulse) trigger-off timeout
When one read per cycle is selected, the device decodes only one
code during the ON period and immediately turns the reader OFF. It is
only possible to read another code when the next ON time occurs. In
multiple reads per cycle, the ON period is extended so that the device
can continue decoding codes until an OFF event occurs. For software
trigger mode, the flash on period is immediately reset after each read
and therefore extended. If another code is decoded before the reset
flash on period expires, it is again reset and the effect is that the device
remains ON, decoding codes until the flash on or timeout period expires.
The safety time parameter should be used in this case to avoid unwanted
multiple reading of the same code.
Safety time
Safety time prevents the device from immediately decoding the same
code more than once. Same code consecutive reading can be disabled
requiring the reader to be removed from the code (no decoding) for
at least 400 ms, or a timeout can be set up to 9.9 seconds before the
decoder will accept the same code. Reading is immediate if the code
changes. The safety time parameter is not applicable when reading
stacked codes or when setting one read per cycle in hardware trigger
operating mode, since these settings require voluntary action by the
user.
Decoding parameters
These parameters are intended to enhance the decoding
capability of the reader for particular applications. Used
incorrectly, they can degrade the reading performance or
increase the possibility of a decoding error.
Ink-spread
The ink-spread parameter allows the decoding of codes that are not
perfectly printed because the page texture tends to absorb the ink.
Overflow control
The overflow control parameter can be disabled when decoding codes
printed on small surfaces that do not allow the use of an overflow space.
This command does not affect code families 2/5, Code 128, and
Code 93.
Interdigit control
The interdigit control parameter verifies the interdigit spacing for code
families Code 39 and Codabar.
Warning
PSCAN-D-1D-D2