Serial I/O (SIO) Digital Inputs and Outputs

Special external digital input and output boards with serial interfaces (SIO devices) can be used to expand the I/O capabilities of a PreciseFlex™ Controller by adding general and dedicated digital inputs and outputs to the system I/O signal map. Their hardware interface consists of a multi-drop RS485 connection to the controller over which is executed a proprietary communications protocol. One or more external I/O interface boards can simultaneously use this interface. An example of such a device is the PrecisePlace 2x00 robot's Z-axis I/O board (ZIO2).

The additional DIO signals only appear as installed when the corresponding SIO device is connected to the controller, configured, enabled and scanning. If the SIO device fails or is disabled, the signals are automatically uninstalled, and any programs that refer to them receive an exception when the uninstalled DIO are accessed.

Configuration

The SIO devices are configured using the configuration parameters shown in the table below:

Parameter Database ID	Parameter Name	Default Value	Description
570	SIO poll period in sec	0.004	This parameter specifies the polling period, in seconds, for all SIO devices. Once each polling period, a message is sent to each external SIO device and a reply is expected. If no reply is received within 8 polling periods, a timeout error is counted. If 3 successive timeouts occur on the same device, the signals associated with the device are uninstalled and depending on the "SIO mode flags" (DataID 571) setting, the robot power is optionally disabled. The polling value must be long enough to allow all devices to be polled and to respond, but should be short enough to allow good I/O signal response. Values from 0.004 to 0.016 are typical.
571	SIO mode flags		An array of numeric values that contain bit flags that specify the operating modes for individual SIO devices. The SIO device unit number is the array index. For example, the ZIO2 board is unit 1 and is accessed as element 1 of this array. The bit flags are defined as follows: &H01 If set, the device is enabled and scans at the polling rate. If not set, the device is not scanned and the associated signals are uninstalled. You must set this bit to make use of the SIO device I/O signals. &H02 If set, robot power on the local controller is turned off and kept off if the SIO device is not responding. This bit should be set for critical I/O points where failure must stop the robot. &H04 If set, the digital outputs on the remote device are set to zero if communications fails. If not set, the digital outputs are frozen if communications fails.
572	SIO error status	0	An array of numeric values that contains the GPL error status for individual SIO devices. The SIO device unit number is the array index. A zero value indicates there is no error. Otherwise the value is a standard GPL negative error code.