JED
RS232 to RS485 (& RS422)
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JED
RS232 to RS485 (& RS422)
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1. JED RS232 to RS485 converter, J995X, with automatic "TX connect-to-line" function for the transmitter, so it does not need special driving software to transmit from a PC to a multi-drop RS485 line. This is ideal for operation from Windows and other software which has difficulty in accessing the driving logic behind the RTS line drivers.
Links provide for baud rate selection, transmit byte length selection, RX line biasing, line termination, and optional RX blanking during transmission.
A recent software revision allows the transmitter to be always enabled, so for 4-wire operation, with one pair always transmitting and one pair always receiving, a two way long distance data communications channel can be set up, equivalent to RS422 standards.
A data sheet is at: J995X.pdf (101KB) or J995X.ZIP (34KB). A close-up photo is at J995X.jpg, (34KB). It is priced at $A160 (plus $A16 GST). An optional 9 volt plug pack is $A20 (plus $A2 GST).
2. JED J995A, our original RS232/RS485 converter, which uses the RS232 RTS line going HIGH to turn on the RS485 transmitter.
Links provide for RX line biasing, line termination, and optional RX blanking during transmission.
The data-sheet is at: J995A.pdf (54KB), or J995A.ZIP (33KB). The photo is at J995A.jpg (25KB). This unit is priced at $A140 (plus $A14 GST). An optional 9 volt plug pack is $A20 (plus $A2 GST). See National Semiconductor's application notes for RS485 via link: National Applications.
(JED makes a number of other RS232 and TTL/CMOS to RS485 converters, with various power options and I/O options (B, C, D, E, F......) Call JED for specific requirements...we can probably do it.)
3. JED RS232 to 20mA isolator, J990, a bi-directional interface from a PC to a 20mA signalling loop. This is useful for interfacing to PLC and other industrial systems from a PC or terminal. While this is an old standard, it is still in occasional use, and JED still supports it with this box.
The data-sheet is at J990.pdf (105KB) or J990.ZIP (44KB). A photo of the J990 is at J990.jpg, (30KB).
4. PC564,
a
new PC/104 quad 550 UART 
serial
interface board. This includes a powerful decoder and interrupt control
EPLD with a variety of interrupt sharing schemes selected with a DIP switch.
One channel on the base PC564 can also communicate via RS485 (2 wire).
The PC564 can also host up to three J995P opto-isolated automatic RS485
interfaces. These mount on the PC654 (still inside the PC/104 profile)
and provide two-wire or four-wire connections on a plug-in Phoenix 5-pin
connector. Each J995P has its own PIC microprocessor to control the TX-ON
of the RS485 transmitter, allowing this card to automatically sense the
start of a transmitted character without the host having to know the exact
time data transmission starts and data then clears the UART's shift
register. This is the same as the JED J995X (above). (Status: in prototype
test.) A photo is now available:
PC564.jpg
Latest update Oct 16th, 2000
