All string registers return empty or garbled values. Why?

SunSpec strings are UTF-8 encoded and null-padded to their full declared length. Some Modbus clients that do not strip trailing null bytes display garbage. Verify your gateway firmware handles null-terminated SunSpec strings correctly, and read the full register width declared in the model block length register l.

The gateway connects but no register values appear at all.

SunSpec Model 16 is positioned at a dynamic offset within the device Modbus map, not at a fixed absolute address. The model block starts where the device places it after the SunS marker and Common Model. Scan from the SunS marker at address 0, 40000, or 50000 to locate the correct base address before applying this template.

Writing to addr, msk, or gw caused the device to go offline.

Writing network configuration registers such as addr, msk, gw, dns1, dns2, or lnkctl takes effect immediately on many devices and will disconnect the device from the network if incorrect values are written. Always prepare and verify new settings before writing. Have physical access arranged as a fallback before making any write operations.

The cfg register reads an unexpected numeric code. What does it mean?

The cfg register is an enumeration where each numeric value represents an IP assignment mode, typically 0 for unknown, 1 for DHCP, and 2 for static. The exact symbol mapping is defined in the SunSpec Model 16 SMDX specification. Cross-check the raw value against that table to determine the current mode.

Free Modbus template: SunSpec Model 16 — Simple IP Network

Name: SunSpec Model 16 — Simple IP Network
Brand: SunSpec
SKU: 5c03e9d1-415e-4ee7-a3a2-fdee21cebf48

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Free Modbus template: SunSpec Model 16 — Simple IP Network | ModbusCloud

Registers (11)

11 read / 8 write

Name	Address	Function	Type	Access
id SunSpec model identifier, fixed value 16 for this model.	0	FC03	uint16	R
l Model block length in 16-bit registers, excluding id and l.	1	FC03	uint16	R
nam Network interface name, user-assigned label string.	2	FC03	string	R/W
cfg IP configuration mode, e.g. DHCP or static assignment.	6	FC03	uint16	R
ctl Network interface enable control, true to activate the interface.	7	FC03	bool	R/W
addr IPv4 address assigned to the network interface, string format.	8	FC03	string	R/W
msk IPv4 subnet mask for the network interface, string format.	16	FC03	string	R/W
gw Default gateway IPv4 address, string format.	24	FC03	string	R/W
dns1 Primary DNS server IPv4 address, string format.	32	FC03	string	R/W
dns2 Secondary DNS server IPv4 address, string format.	40	FC03	string	R/W
lnkctl Physical link control flag, enables or disables the network link.	52	FC03	bool	R/W