Appendix A: Modbus Register Map¶

Source: Eastron SDM630MCT Modbus Protocol V1.7

Communication Parameters¶

Parameter	Default
Protocol	Modbus RTU
Baud rate	9600 bps
Data bits	8
Parity	EVEN
Stop bits	1
Byte order	Big-endian (ABCD)
Float format	IEEE 754 (32-bit)

Input Registers (Function Code 04)¶

All values are 32-bit IEEE 754 floats occupying 2 consecutive registers.

Voltage Registers¶

Address	Hex	Parameter	Unit	3P4W	3P3W	1P2W
30001	0x7531	Phase 1 line to neutral volts	V	✓	✓	✓
30003	0x7533	Phase 2 line to neutral volts	V	✓	✓	—
30005	0x7535	Phase 3 line to neutral volts	V	✓	—	—
30007	0x7537	Phase 1 line to line volts	V	✓	✓	—
30009	0x7539	Phase 2 line to line volts	V	✓	✓	—
30011	0x753B	Phase 3 line to line volts	V	✓	✓	—

Current Registers¶

Address	Hex	Parameter	Unit	3P4W	3P3W	1P2W
30013	0x753D	Phase 1 current	A	✓	✓	✓
30015	0x753F	Phase 2 current	A	✓	✓	—
30017	0x7541	Phase 3 current	A	✓	—	—
30019	0x7543	Neutral current	A	✓	—	—

Power Registers¶

Address	Hex	Parameter	Unit	3P4W	3P3W	1P2W
30021	0x7545	Phase 1 active power	W	✓	✓	✓
30023	0x7547	Phase 2 active power	W	✓	✓	—
30025	0x7549	Phase 3 active power	W	✓	—	—
30027	0x754B	Total active power	W	✓	✓	✓
30029	0x754D	Phase 1 reactive power	VAr	✓	✓	✓
30031	0x754F	Phase 2 reactive power	VAr	✓	✓	—
30033	0x7551	Phase 3 reactive power	VAr	✓	—	—
30035	0x7553	Total reactive power	VAr	✓	✓	✓
30037	0x7555	Phase 1 apparent power	VA	✓	✓	✓
30039	0x7557	Phase 2 apparent power	VA	✓	✓	—
30041	0x7559	Phase 3 apparent power	VA	✓	—	—
30043	0x755B	Total apparent power	VA	✓	✓	✓

Power Factor & Frequency¶

Address	Hex	Parameter	Unit	3P4W	3P3W	1P2W
30045	0x755D	Phase 1 power factor	—	✓	✓	✓
30047	0x755F	Phase 2 power factor	—	✓	✓	—
30049	0x7561	Phase 3 power factor	—	✓	—	—
30051	0x7563	Total power factor	—	✓	✓	✓
30053	0x7565	Phase angle L1	Degrees	✓	✓	✓
30055	0x7567	Phase angle L2	Degrees	✓	✓	—
30057	0x7569	Phase angle L3	Degrees	✓	—	—
30059	0x756B	Total phase angle	Degrees	✓	✓	✓
30061	0x756D	Frequency	Hz	✓	✓	✓

Energy Registers¶

Address	Hex	Parameter	Unit	3P4W	3P3W	1P2W
30063	0x756F	Import active energy	kWh	✓	✓	✓
30065	0x7571	Export active energy	kWh	✓	✓	✓
30067	0x7573	Import reactive energy	kVArh	✓	✓	✓
30069	0x7575	Export reactive energy	kVArh	✓	✓	✓
30071	0x7577	Total active energy	kWh	✓	✓	✓
30073	0x7579	Total reactive energy	kVArh	✓	✓	✓

Demand Registers¶

Address	Hex	Parameter	Unit
30075	0x757B	Total system power demand	W
30077	0x757D	Maximum total system power demand	W
30079	0x757F	Phase 1 current demand	A
30081	0x7581	Maximum Phase 1 current demand	A
30083	0x7583	Phase 2 current demand	A
30085	0x7585	Maximum Phase 2 current demand	A
30087	0x7587	Phase 3 current demand	A
30089	0x7589	Maximum Phase 3 current demand	A

Total Harmonic Distortion¶

Address	Hex	Parameter	Unit
30091	0x758B	Phase 1 voltage THD	%
30093	0x758D	Phase 2 voltage THD	%
30095	0x758F	Phase 3 voltage THD	%
30097	0x7591	Phase 1 current THD	%
30099	0x7593	Phase 2 current THD	%
30101	0x7595	Phase 3 current THD	%

Holding Registers (Function Code 03/16)¶

Configuration Registers¶

Address	Hex	Parameter	Range	Mode	Default
40001	0x9C41	Reset demand / energy	1=reset	wo	—
40063	0x9C7F	CT ratio (per phase)	1–2000	r/w	1
40065	0x9C81	PT ratio	1–4000	r/w	1
40069	0x9C85	Baud rate	0=2400, 1=4800, 2=9600, 3=19200, 4=38400	r/w	2
40071	0x9C87	Modbus address	1–247	r/w	1
40073	0x9C89	Parity	0=EVEN, 1=ODD, 2=NONE	r/w	0
40079	0x9C8F	Pulse output 1 mode	See table	r/w	0
40081	0x9C91	Pulse output 2 mode	See table	r/w	2
40083	0x9C93	Pulse width	30–61440 ms	r/w	60
40085	0x9C95	DIT (demand integration time)	1–60 min	r/w	15
40089	0x9C99	Backlit timeout	0–255 min	r/w	5
40091	0x9C9B	Setup password	0–9999	r/w	1000
40093	0x9C9D	Network relay pulse output 1	—	r/w	—
40095	0x9C9F	Network relay pulse output 2	—	r/w	—

Pulse Output Mode Values¶

Value	Pulse 1 Meaning	Pulse 2 Meaning
0	Import active energy	Import reactive energy
1	Export active energy	Export reactive energy
2	Import + Export active	Import + Export reactive

Modbus RTU Frame Format¶

Request Frame (Read Input Registers)¶

[Address][Function][Register Hi][Register Lo][Count Hi][Count Lo][CRC Lo][CRC Hi]
  01       04        00         00          00        02        xx      xx

Response Frame¶

[Address][Function][Byte Count][Data Hi][Data Lo][Data Hi][Data Lo][CRC Lo][CRC Hi]
  01       04        04         xx      xx      xx      xx      xx      xx

CRC-16 Calculation¶

Modbus RTU uses CRC-16 (Modbus variant). Most Modbus libraries handle this automatically.

RS485 Wiring Specifications¶

Parameter	Value
Cable type	Twisted pair (shielded recommended)
Bus length (max)	1200 meters
Devices per bus (max)	32
Termination	120Ω at each end of bus
Connectors	Screw terminals (9=D+, 10=D-)