sorry, Harry, I misunderstood you ...
from harryting:
Hey Ron, you mind expand on that a bit? Thanks.
when I first read this it looked like Harry had said: “Do you mind if I (Harry) expand on that subject?” ... but now that I look at it again it is obvious that Harry was asking me (Ron) to dig a little bit deeper into this matter ... oops ... but, Harry, you should have said “expandING” ... just another failure to communicate ...
I’m sorry that I don’t have time to do this subject justice tonight but I’ll give it a shot just as a starter ... disclaimer: some of what follows is (over) simplified ... I apologize in advance for any confusion that this might cause but this is intended to be just a basic “getting started” discussion ...
in post #9 I said:
you don't ALWAYS need a 1747-PIC (hardware) in order to use the 1747-PIC driver (software) ...
when I made that statement I had the following points in mind ... the SLC-5/03, SLC-5/04, and SLC-5/05 processors have an RS-232 port available ... this port has a male DB-9 connector ... on the configuration screen, this port is referred to as “Channel 0” ...
this port is generally (and by default) set up for “DF1 Full Duplex” ... but this same port can also be set up (as it was in hhuong’s case) for “DH-485” (Data Highway 485) ... this is basically an Allen-Bradley networking configuration ... it was (as I understand) originally designed to be cheaper to implement than its big brother the DH+ (Data Highway Plus) network ...
now to the point ... the term “DH-485” has TWO distinct parts ...
one part of the term “DH-485” refers to the physical “hardware” used to implement the communication connection ...
the other part of the term “DH-485” refers to the “protocol” used to implement the communication ...
an analogy:
suppose that we go to Germany and examine their telephone communication system ... suppose that the telephone lines in Germany are designed to operate at 5 volts DC ... the language spoken on the German telephone lines is (of course) German ...
now suppose that we go to Italy and examine their telephone communication system ... suppose that the telephone lines in Italy are designed to operate at 24 volts DC ... the language spoken on the Italian telephone lines is (of course) Italian ...
in this simple analogy, we could talk about the “German” telephone system and have in mind BOTH the “hardware” (5 volts) specification AND the “protocol” (German language) specification of the system ... and also ... we could talk about the “Italian” telephone system and have in mind BOTH the “hardware” (24 volts) specification AND the “protocol” (Italian language) specification of the system ...
completing the analogy:
the common “RS-232/DF1” configuration refers to both a “hardware” (voltage) specification ... and to a “protocol” (language) specification ...
the less-common “DH-485” configuration refers to both a “hardware” (voltage) specification ... and to a “protocol” (language) specification ...
normally (but not always) the “hardware” (voltage) specification and the “protocol” (language) specification “GO TOGETHER” ... specifically ...
the “hardware” (voltage) of the “RS-232/DF1” specification is NORMALLY used with the “protocol” (language) of the same “RS-232/DF1” specification ... and ...
the “hardware” (voltage) of the “DH-485” specification is NORMALLY used with the “protocol” (language) of the same “DH-485” specification ... but ...
SOMETIMES one “hardware” (voltage) specification can be “mixed-and-matched” with the OTHER “protocol” (language) specification ... and that’s what was happening to our friend hhuong ...
now to the 1747-PIC “adapter” ... this “adapter” is a physical piece of “hardware” ... basically it’s a gray plastic box with two cables attached ... it’s primary use is to convert the RS-232 voltage levels from the back of your programming computer to the higher voltage levels used for the RJ-45 connector on the front of some SLC processors (SLC-500, SLC-5/01, SLC-5/02, and SLC-5/03) ... this conversion of the voltage levels MUST be done by a piece of hardware ... consider the telephone analogy ... there is NO WAY to simply “plug in” a German telephone set (5 volts) to the Italian telephone system (24 volts) and expect it to work properly ... to use a German telephone set in Italy would require a physical “adapter” of some sort to convert from one voltage level to the other ...
now to the 1747-PIC “driver” ... this “driver” is a “software” program ... it’s included as part of the RSLinx package ... it’s primary use is to convert the RS-232 “language” from the back of your programming computer to the DH-485 “native language” used by some SLC processors (SLC-500, SLC-5/01, SLC-5/02, and SLC-5/03) ... consider the telephone analogy ... we cannot simply “speak” German on the Italian telephone system and be understood ... to speak German on the Italian telephone system would require a “translator” of some sort to convert from one language to the other ...
and so to nail this down ... the 1747-PIC “adapter” is a piece of hardware for the DH-485 system ... the 1747-PIC “driver” is a piece of software for the DH-485 system ...
now ... sometimes the “Channel 0” DB-9 port on the front of an SLC processor is set up (as it was in hhoung’s case) for “DH-485” ... when that happens the voltage levels on the DB-9 port do NOT change ... specifically the port’s voltage levels stay perfectly compatible with the voltage levels used on your programming computer’s RS-232 (serial) port ... no problem there ... and specifically we do NOT need a 1747-PIC adapter ... the same old three-wire null modem cable that we usually use for this port will still work just fine ...
but ...
when the “Channel 0” port is set up for “DH-485” communications, the “protocol” (the language being spoken) DOES change ... specifically the port’s protocol (language) is no longer “DF1” ... and that’s a BIG problem if you’re still trying to use the old familiar “RS-232/DF1 Full Duplex” driver ... the solution is to use the 1747-PIC “driver” instead ... this SOFTWARE speaks a “protocol” (language) which is compatible with the DH-485 setting of the “Channel 0” port ...
and that’s the best I can do for tonight ... I welcome others to correct the “simplifications” that I made above ... but I’ve tried to keep this at a “let’s-get-started” level ... I hope that it helps ...
and one more thing ... this might help decide which driver (the “RS-232/DF1” or the “1747-PIC”) you need to use ... with NO cable connected to the DB-9 port, watch the LED marked “RS-232” on the front of the processor ... if it flashes about once every four seconds, then the DB-9 port is (probably) set for “DH-485” and you’ll (probably) need the “1747-PIC” driver in RSLinx ... but if there is NO flashing, then the DB-9 port is (probably) set for “DF1 Full Duplex” and you’ll (probably) need the “RS-232/DF1” driver in RSLinx ...