SNP Protocol

SNP ID

When the SNP ID is entered, a six digit ID with leading zeros is created. For example if the ID “12” is entered, the SNP ID in your device should be set to “000012”. Entering an ID of “0” will create a NULL SNP ID where all six ID characters should be set to NULL.

CSCAPE Configuration

To configure OCS for the SNP protocol, select the Protocol Configuration from the Program menu in CSCAPE software. Select the appropriate protocol type in desired port. To make sure that the Software is able to configure the equipment for the correct protocol, make sure Snp.dll file is in the Protocols directory of the current working/open Cscape.

Configuring GE SNP Device

Following are the steps for configuring GE SNP with Cscape application:

Open Program > Protocol Config and perform the following configurations:

Step 1: Select GE SNP (Series 90 Protocol) from the drop-down list.

Step 2: On network configuration dialog user can configure following network parameters/status registers.

Configure Baud Rate, Parity, Stop Bits, Handshake, Protocol (SNP), RS-232/485, Retries and Timeout.
Configure the update Scan type as automatic or manual according to process requirements.
Configure the (optional/recommended) network status register.

Step 3: Click Devices button to configure Slave device (0-255) as follows:

Configure slave device name and ID.

If option for Swap Words on 32-bit Data is checked, the high and low 16-bit values of 32-bit Data are swapped when transferred between the target and OCS.

Device status registers can be optionally enabled and used to determine the current state of communications.

Select Stop on Error or Retry on Error as per process requirement.

Step 4: Click Scan List button to configure Data Mapping.

To transfer data between the OCS and remote target, a Scan List must be created that defines each transaction. Each mapping entry (transaction) contains the source and destination registers, the number of consecutive registers transferred, the direction of the transfer and trigger for transfer (optional).

Entering Registers

Registers should be entered with the “%” prefix, the type should be in uppercase and the type and range should follow the chart below.

REGISTER	Type	Start	End
DATA	%R	1	16384
RELAY	%M	1	32768
INPUT	%I	1	32768
OUTPUT	%Q	1	32768
TEMPORARY	%T	1	512
ANALOG INPUTS	%AI	1	8192
ANALOG OUTPUTS	%AQ	1	8192
DISCRETE SA	%SA	1	256
DISCRETE SB	%SB	1	256
DISCRETE SC	%SC	1	256
DISCRETE S	%S	1	256
GENIUS GLOBALS	%G	1	7680

Network Communication Errors

In order to access the Network statistics, user must assign the “Network status register” in network configuration. The table below gives the details of statistics.

Number	Statistics	Location	Description

1	Update interval exceeded count	%Rx	This register explains number of times that the actual transaction scan time to complete all transactions exceeded specified update interval. Generally used as an indicator that an excessive number of triggered transfers or failed communication retries are occurring that is lengthening the expected transaction scan time. If the Update interval is set to zero (update as fast as possible), this 32-bit register alternately specifies the actual transaction scan time in mSec resolution.
2	No response count	%R(x+2)	This register explains number of times that a device(s) did not respond to a transaction. This includes ALL failed transaction, not just those after the retry count is exceeded.
3	Corrupt Response Count	%R(x+4)	This register explains number of times that a device(s) returned an invalid or failed response to a transaction. This includes ALL failed. Transaction, not just those after the retry count is exceeded.
4	Valid Response Count	%R(x+6)	This register explains total number of valid responses.

NOTE: %Rx: 32-bit network status register configured in Network configuration. For example: %R500(501).

Device Communication Errors

Error	Error Number	Description
INVALID_BLOCK	-203	Invalid size for data type.
NO_RESPONSE_FROM_PLC	-204	Timeout while waiting for remote node response.
INVALID_RESPONSE_FROM_PLC	-205	Corrupted response from remote node.
INVALID_INITIALISATION	-207	Internal Error - Unable to open port.