Programming instructions

80
Intermec Fingerprint 6.13 – Programmer's Guide
• Multidrop Loop, cont'd.
Set the printer's flowcontrol setup parameters as follows:
RTS/CTS: Always Disable
ENQ/ACK: Always Disable
XON/XOFF, Data from host:Always Disable
XON/XOFF, Data to host: Always Disable
Prot. addr: Enable
Set verbosity to off using a VERBOFF statement or a SYSVAR(18)=0 instruction.
Master Unit
The master unit controls the data flow in the loop and must always
have address 0.
In case of using a computer as master, refer to the computer's
manual for information on how to appoint the computer master
and how to set its address to 0.
In case of using a printer as master (e.g. in a printers-only loop),
the address 0 must be strapped and two voltage reference straps
must be fitted on the printer's RS 422/485 interface board.
Example showing communication between master and a slave
with the address 8:
OPEN "rs485:8" FOR OUTPUT AS #1
OPEN "rs485:8" FOR INPUT AS #2
PRINT #1,"SEND STATUS" (a status request is sent to Slave No. 8)
LINE INPUT #2, A$ (message is read from Slave No. 8)
.....
Slave Units
Commonly, the master in a loop is a computer and the slaves are
printers, each with an individual address (1–31).
The computer controls the data flow by sending data to a specified
printer, or by sending a request to check if the master needs any
data from the printer. An application program must be created that
defines a protocol within the data record, which defines when a
slave is allowed to send data.
In the program of the slave printer, rs485 is OPENed for both input
and output. No destination address is required in the OPEN
statement, since address 0 (i.e. master) is automatically assumed.
When a complete packet of data is available, the application
program is able to read the data record sent from the master. If the
data is a status request, the printer can send data back to the master.
The header record will automatically be added to the packet.
Example showing communication between slave and master:
OPEN "rs485:" FOR INPUT AS #1
OPEN "rs485:" FOR OUTPUT AS #2
LINE INPUT #1,A$ (data from master are read)
PRINT #2, "DATA TO MASTER" (data are sent to master)
.....
9. RS 422/485
Communication, cont'd.
7. INPUT TO FINGERPRINT, cont'd.
Continued!