Setting the CNC

Most CNC units use several "parameter" registers to configure the CNC's RS-232 port. Changing the parameters is usually done by entering new data at the CNC keyboard in the manual data input mode. For more information about how to change the parameter settings, refer to your CNC's user manual. It is very important that the baudrate setting of the CNC unit matches the baudrate used in Inplot.


The four most common types of Fanuc CNCs are:

1) System 3 series (3T, 3M, 3TF, etc.)

2) System 6 series (6T, 6M)

3) System 6-B series (6TB, 6TF, 6MB, 6MF, etc.)

4) System 10/11/12/15 series (all variations)

5) System 0 (0TA, 0TB, 0TC, 0MA, 0MB, and 0MC)

Each series has a different set of parameters for the RS-232 port.


System 3 series:

a) Set baudrate with parameter #68 and #69 (set both to 300)

b) Set parameters 5 and 14 to: 1xxxx0x0 (bits marked "x" are

used for something else - do not change).

c) Other SETTING values: Punch Code = ISO, I/O device = 0


System 6A series (6T,6M - older models):

a) Set baudrate with parameter #25 (10001100 = 300 baud)

b) Set parameter #24 to: xxxxxxx0 (don't change bits with "x")

c) Set parameter #26 to: 0xxxxxxx " " " "

d) Other SETTING values: Punch code = ISO, INPUT DEVICE 2 = 1


System 6B series (6TB, 6MB, and so on):

a) Set baudrate with parameter #311 (11000101 = 300 baud)

b) Set parameters 340 and 341 to: 2

c) Other SETTING values: Punch code = ISO, INPUT DEVICE 2 = 1


System 10/11/12/15 series:

a) Set parameters 5110, 5120 and 5130 to : 3 (I/O type)

b) Set parameters 5111, 5121 and 5131 to : 1 (stop-bits)

c) Set parameters 5112, 5122 and 5132 to : 6 (300 baud)

d) Set parameter 0000 to: xxx01010 (disregard bits marked "x")




System 0 series

a) Set parameters 0002 and 0012 to: 1xxxx0x0

b) Set parameters 553 and 554 to: 6 (300 baud)

c) Other SETTING values: PUNCH CODE = ISO, I/O = 1



Making the cable

Most CNC units, tape punch/readers and computers use the standard DTE (Data Terminal Equipment) pin assignments on the RS-232 plug. When connecting two DTE devices together (such as hooking the personal computer to a Fanuc control unit) you must "cross-connect" some wires as shown in Figure 1. When connecting the personal computer to a DSI tape punch/reader, use the MODEM plug on the back of the tape punch/reader. Use only high quality shielded cable with 22 or 24 gage stranded wires.

Some personal computers will have a 9-pin male plug instead of a standard 25-pin plug for the RS-232 serial port. If your computer has a 9-pin plug, use a 9 to 25 pin adapter, sometimes called an "AT serial port adapter". These adapters are readily available for about $5 at Radio Shack, and are used with the cable described below.



male for Fanuc CNC side --------------------------------- female for PC side


2 *--------------------------* 3

3 *--------------------------* 2

4 *--------------------------* 5

5 *--------------------------* 4

7 *--------------------------* 7

6*------ Tie pins 6, 8, and 20 together on CNC side





If your personal computer and CNC machine tool are compatible with those mentioned in this article, and if you have followed the instructions carefully, your DNC link should be successful. If not, double check the procedure to be sure you have not missed a step. Here is a list of a few typical problems and their possible solutions.

1) If no data is transferred in either direction and a "Device I/O error occurs on the PC, you probably have a baudrate or "stop" bits mis-match between devices. Confirm that your CNC or punch reader is using the baudrate you expect.

2) If no data is transferred in either direction and no errors occur, you may have an improperly wired cable. If your CNC or puncher uses a DCE port instead of the usual DTE port, you must use a "straight through" cable instead of the cross-wired type described above.

3) If a "Communications Buffer Overflow" error occurs on the PC, your CNC is probably ignoring the handshaking signals CTS and DSR (pins 5 and 6) and is sending data when not ready.

4) Some tape punch/readers (Blue Chip, for example) must use 2 "stop" bits for all communications. Also, most devices that operate at 110 baud use 2 "stop" bits.

5) Some controls (early model Bridgeports) use ASCII code without a "parity" bit (channel #8 on a paper tape).

6) A very few Fanuc CNCs were not able to send programs in ISO code even though the setting parameter labeled "PUNCH CODE" is set for ISO (EIA/ISO switching is an optional feature).

Back to Index