RS232 Setup

RS232 connector pinouts

The PHC10-3 communicates with the CMM computer via the RS232 cable as shown in the table below.

2Transmitted data (Tx) to CMM computer
3Received data (Rx) from CMM computer
4RTS (Request to send) to CMM computer +12V after initialisation routine completed

CTS (Clear to send) from CMM computer.
CMM computer disasserts CTS to halt PHC10-3 transmitions
Connect pin 5 to pin 20 if CTS is not output from the CMM computer

7Signal ground (common)
20DTR (Data terminal ready) to CMM computer signifies PHC10-3 power ON condition

Baud rate selection

The baud rate is set using switches 1 to 3 as shown in the table below:

Baud rateSwitch 1Switch 2Switch 3


CAUTION: The PHC10-3 must be powered down and then powered up to allow any changes to the rear panel switch settings to take effect.

Protocol selection

The PHC10-3 has two switch-settable command sets (basic command set and extended command set) offering different protocol options. The command set selection is made using switch 9 on the rear panel.

9UPExtended command set mode (recs)
9DOWNBasic command set mode

Basic command set mode

In this mode the PHC10-3 is fully compatible with existing integration methods in terms of communications protocols, software command set and RS232 protocol options.

Basic command set protocol


4UP2 stop bits
4DOWN1 stop bit
5UPCTS (Clear to send) ON
5DOWNCTS (Clear to send) OFF
6UPLF (Line feed) ON
6DOWNLF (Line feed) OFF

 Data transmission format is as follows:

  • 1 start bit
  • 7 data bits
  • 1 parity bit (ignored on Rx: always 0 on Tx)
  • 1 or 2 stop bits (switch 4)

Protocols: PHC10-3 RTS is asserted before first transmission from the head and remains asserted. If switch 5 is UP, CTS must be asserted by the CMM computer to allow the head to transmit. If switch 6 is UP, the PHC10-3 will add an ASCII LF character to every transmitted message.

Extended command set mode

In this mode the PHC10-3 uses the Renishaw extended command set. It is completely different from and incompatible with the basic command set. The RS232 protocol is fixed with no user selectable options other than baud rate. The extended command set offers the following advantages over the basic command set:

• Software control of the hand control unit (HCU1) functions such as jog and sweep

• Software control of selected PICS (product interconnection system) functions such as probe damping, Probe Power OFF and LED OFF

• Software control of selected probe functions (TP200 probe reset)

• Common communications protocol for products using the extended command set

• As probing systems become increasingly sophisticated and offer a wider range of functions and control options, they will be incorporated into the new command structure, reducing integration times and costs for CMM manufacturers

• The introduction of product identifiers and device numbers will enable control of multiple Renishaw interfaces in future implementations of the extended command set

Please contact Renishaw for further details of the extended command set. 

NOTE: The functions of switches 4, 5 and 6 will have no effect on the system when switch 9 is UP 

In extended command set mode, the data transmission and protocol formats are fixed in line with modem RS232 conventions. There are no user selectable options.

Data transmission format is as follows:

  • 1 start bit
  • 7 data bits
  • 1 even parity bit
  • 1 stop bit


  • PHC10-3 RTS is normally asserted. It is unasserted when the PHC10-3 is unable to receive further transmissions.
  • The PHC10-3 CTS must be asserted (by the CMM computer, or by linking DTR to CTS) to allow the PHC10-3 to transmit.


  • The extended command set supports the use of XON/XOFF flow control by the CMM computer.
  • If the PHC10-3 receives an XOFF character, PHC10-3 transmissions will cease and be buffered until an XON character is received by the PHC10-3 or the output buffer overflows.
  • It is possible to continue transmissions to the PHC10-3 while it is in the XOFF state, although this is not recommended as it may cause overflow of the output buffer, resulting in lost responses.