GE SRTP (GE Fanuc / PACSystems)

SRTP (Service Request Transport Protocol) is the standard communication protocol for GE Fanuc / Emerson PACSystems / GE RX3i / RX7i / VersaMax series PLCs. These PLCs are commonly encountered in the U.S. automation market (automotive, aerospace, power generation).

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Registration Form Input Values

Input Field	What to Enter	Example
IP Address	PLC IP	192.168.0.150
Port	SRTP port	18245 (standard / change not recommended)
Response Timeout (request-timeout)	Response wait time (ms)	5000

GE PLCs communicate without a separate username/password. SRTP communication must be enabled on the PLC side in Proficy Machine Edition or PAC Productivity Suite.

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PLC Address Notation for Tags

GE PLCs use % + letter + number format for memory areas. It looks similar to Siemens, but the area letters are different.

Notation	Area	Notes
%R100	Register Memory 100	Most common, 16-bit
%I100	Discrete Input 100	1 bit
%Q100	Discrete Output 100	1 bit
%T100	Temporary Reference 100	1 bit
%M100	Internal Memory 100	1 bit
%S100	System Reference	1 bit
%G100	Global Memory	1 bit
%AI100	Analog Input 100	16-bit
%AQ100	Analog Output 100	16-bit
%W100	Word Memory	16-bit

Combining for 32-bit / Floating Point

%R100 is one 16-bit slot. 32-bit integer / floating point uses two slots combined (%R100 + %R101), with the width specified via [Format Helper].

Notation	Meaning
%R100	16-bit integer
%R100 + DW	32-bit integer (R100~R101)
%R100 + REAL	32-bit floating point (R100~R101)
%R100 + STR[10]	10-word (= 20 characters) string

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Data Type Matching

PLC Value	Data Type	Format Helper	Example PLC Address
Bit (I, Q, M, T)	Boolean	(empty)	%I100, %Q100, %M100
16-bit integer	Integer	(empty)	%R100, %AI100
16-bit unsigned	Integer	UI	%R100
32-bit integer	Integer	DW	%R100
32-bit unsigned	Integer	UDW	%R100
32-bit floating point (most common)	Float	REAL	%R200
64-bit floating point	Double	LREAL	%R300
String N words	String	STR[N]	%R500

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Common Issues and Solutions

Symptom	Possible Cause	Resolution
"Connection refused"	SRTP port 18245 blocked or SRTP disabled on PLC	Enable SRTP communication in Proficy ME, open firewall port 18245
"Service request error"	Incorrect area letter or number out of range	Use the correct area such as %R / %I / %Q. Verify the number is within the PLC memory size
All values 0	Area mismatch (registered as %AI when it's %R, etc.)	Check the reference table in Proficy to see which area actually contains the data
32-bit values abnormal	Format Helper not set	Specify DW (integer) / REAL (floating point)
Only Bool not reading	Bool registered in %R area	Use bit areas like %I / %Q / %M / %T

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Frequently Used Examples

Tag Name	PLC Address	Data Type	Format Helper
Pump Running	%M100	Boolean	(empty)
Input Signal	%I100	Boolean	(empty)
Output ON	%Q100	Boolean	(empty)
16-bit counter	%R100	Integer	(empty)
32-bit accumulated	%R200	Integer	DW
Pressure (floating point)	%R300	Float	REAL
Batch name (10 words)	%R500	String	STR[10]

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Next Steps

• The reference table in Proficy Machine Edition / PAC Productivity Suite is the most accurate address source.
• Refer to the GE example in Advanced — REST API.