RS-485 DB9 cables, wired the way your device is.
RS-485 has no standard DB9 pinout, so these follow the two published ones: PROFIBUS (pins 3 and 8) and MODBUS (pins 5 and 9), the data pair twisted. anything else, set your own. genuine Amphenol parts · priced instantly · free 2-day shipping.
Price
both conventions, priced.
| build | qty 1, each | qty 10, each | qty 50, each | configure |
|---|---|---|---|---|
| PROFIBUS pins: B/A twisted (3, 8) + DGND (5), 12 in (305 mm) | $40.00order minimum | $23.26 | $22.03 | configure |
| PROFIBUS pins: B/A twisted + DGND, 24 in (610 mm) | $40.00order minimum | $25.31 | $23.98 | configure |
| MODBUS 2-wire: D1/D0 twisted (5, 9) + common (1), 12 in (305 mm) | $40.00order minimum | $23.26 | $22.03 | configure |
| MODBUS 4-wire, straight for slave drops: two twisted pairs (5/9, 4/8) + common, 12 in (305 mm) | $40.00order minimum | $30.32 | $28.73 | configure |
| PROFIBUS B, A, DGND to 12 in (305 mm) leads with ferrules | $40.00order minimum | $15.63 | $14.81 | configure |
| MODBUS D1, D0, common to 12 in (305 mm) leads with ferrules | $40.00order minimum | $15.63 | $14.81 | configure |
each · free UPS 2-day shipping · $40 order minimum (a smaller order is charged $40) · ships in 10 business days. these are example builds: change the length, pinout and colors in the configurator and it prices the result the same way.
Drawing
the PROFIBUS-pinout cable, pin for pin.
3 wires between two DB9s, 22 AWG in the standard color order, the twisted pair drawn twisted. the configurator draws the same diagram for your own pin map and exports it as a PDF.
| end A | end B | wire |
|---|---|---|
| pin 3 B | pin 3 B | black, twisted pair T1 |
| pin 8 A | pin 8 A | white, twisted pair T1 |
| pin 5 DGND | pin 5 DGND | blue |
Pinout
there's no one RS-485 DB9 pinout.
RS-485 specifies the electrical signal only, not a connector or a pinout. two published conventions put it on a DB9 — and they don't agree on a single pin. here they are side by side; your device's manual says which, if either, it follows.
| pin | RS-485 (PROFIBUS) | RS-485 (MODBUS) |
|---|---|---|
| 1 | not connected | Common |
| 2 | (M24) | (VP) |
| 3 | B | (PMC) |
| 4 | (CNTR-P) | RXD1 |
| 5 | DGND | D1 |
| 6 | VP | not used |
| 7 | (P24) | not used |
| 8 | A | RXD0 |
| 9 | (CNTR-N) | D0 |
sources: Wikipedia, RS-485 ("does not specify any connector or pinout"); PROFIBUS Interconnection Technology guideline v1.4 (2007), table 3.1-1; MODBUS over Serial Line v1.02 (2006) §3.5.1 and §3.5.2.
| pin | signal | what it is | in this build |
|---|---|---|---|
| 1 | — | not connected | not wired |
| 2 | (M24) | ground of the 24 V supply, optional | not wired |
| 3 | B | RxD/TxD-P, receive/transmit data, line B | black wire → pin 3, twisted pair T1 |
| 4 | (CNTR-P) | repeater direction control, optional | not wired |
| 5 | DGND | data ground (reference for VP) | blue wire → pin 5 |
| 6 | VP | +5 V supply, e.g. for bus termination | not wired |
| 7 | (P24) | +24 V supply, optional | not wired |
| 8 | A | RxD/TxD-N, receive/transmit data, line A | white wire → pin 8, twisted pair T1 |
| 9 | (CNTR-N) | repeater direction control, optional | not wired |
Connector
DB9 (DE-9)
Wire
20–24 AWG
Length
5–48 in (127–1219 mm)
Lead time
10 business days
Questions
about the RS-485 DB9 cable.
- can I order just one?
- yes, there's no minimum quantity, but there is a $40 order minimum. one 12 in (305 mm) PROFIBUS-pinout cable comes to $24.48, so an order of just that is $40; add more and the minimum is covered. shipping is free (UPS 2-day). prices drop at 10 and 50 units.
- which pinout does my device use?
- its manual will say. RS-485 defines the electrical signal but no connector or pinout, so DB9 RS-485 ports differ: PROFIBUS devices use pins 3 and 8 with ground on 5, MODBUS's serial-line spec puts the pair on 5 and 9 with common on 1, and plenty of devices use neither. if yours is different, set its pins in the configurator.
- why are A and B sometimes swapped?
- makers don't agree on which line is A and which is B, and many label them the opposite way from the standard's own definition. go by your device's manual; if a link doesn't talk, swapping the pair is the usual first check, and in the configurator it's one change on each end.
- does the 4-wire cable go from the master to a slave?
- not as built. the MODBUS spec gives the master and the slaves the same pinout and says a 4-wire line must cross its two pairs between the bus and the master, so the 4-wire row above runs straight through: it's for slave drops. for the master's cable, wire 5 to 4, 9 to 8, 4 to 5 and 8 to 9 in the configurator.
- why plugs on both ends?
- the MODBUS spec calls for a female connector on the device and a male one on the cable, and the PROFIBUS guideline draws its bus connector as male. switch either end to a receptacle in the configurator if your device differs.
- is it shielded or terminated?
- neither. it's UL1007 hook-up wire with the data pair twisted in the shop, no shield and no termination resistors. the MODBUS spec requires a shielded cable for a MODBUS line, and PROFIBUS terminates both ends of the bus (its guideline's bus connector has the resistors built in), so where either applies, use a rated bus cable and connectors.
- how is it made?
- each wire is tinned and soldered into its contact's solder cup with lead-free solder, then a hood goes over the joints, plastic or zinc, with 4-40 screws to lock it to the mating connector. every cable gets a continuity test.
- what wire gauges and lengths?
- 20, 22, 24 AWG UL1007 hook-up wire, any length, 5–48 in (127–1219 mm). the prices above are at 22 AWG unless a row says otherwise.
- how fast does it ship?
- it's built and shipped in 10 business days, then goes out UPS 2-day.
more in the FAQ, including returns (custom cables are non-returnable; defects replaced).
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