Magnetically Encoded SMSMB Servo - Memory Table¶

For SMSMB series servos, which use the standard MODBUS-RTU protocol. MODBUS holding registers are 16-bit and two-byte fields are transmitted with the high byte first; "Address (PLC)" is the corresponding MODBUS holding-register address (4xxxx).

1 Servo Communication Protocol¶

Servos use the standard MODBUS-RTU protocol. Factory serial defaults: baud rate 115200, 8 data bits, no parity, 1 stop bit; configurable baud rate range 9600~256 Kbps, default communication address (station number) 1.

For the full frame format and instruction set, see Bus Protocol.

2 Servo Memory Table Definition¶

2.1 Version Information¶

Address (DEC)	Address (HEX)	Address (PLC)	Function	Bytes	Initial value	Access
0	0x0	40001	Firmware version	2	–	R
1	0x1	40002	Servo version	2	–	R
2	0x2	40003	Firmware release date (year)	2	–	R
3	0x3	40004	Firmware release date (month)	2	–	R

2.2 EPROM Configuration¶

Address (DEC)	Address (HEX)	Address (PLC)	Function	Bytes	Initial value	Access	Range	Unit	Description
10	0x0A	40011	ID	2	1	R/W	1~247	ID	Unique identifier on the bus; no duplicate ID may appear on the same bus; ID 0 (0x00) is the broadcast ID
11	0x0B	40012	Baud rate	2	2	R/W	0~9	None	0-9 correspond to baud rates: 256000(0), 128000(1), 115200(2), 57600(3), 56000(4), 38400(5), 19200(6), 14400(7), 9600(8), 4800(9)
12	0x0C	40013	Return delay	2	500	R/W	0~500	1us	0 means the minimum return delay; the maximum settable return delay is 500us
13	0x0D	40014	Minimum angle limit	2	0	R/W	0~4095	0.0879°	Sets the lower limit of the travel range; the value must be smaller than the maximum angle limit; 0 in multi-turn absolute position control
14	0x0E	40015	Maximum angle limit	2	4095	R/W	0~4095	0.0879°	Sets the upper limit of the travel range; the value must be greater than the minimum angle limit; 0 in multi-turn absolute position control
15	0x0F	40016	Position calibration	2	0	R/W	-2047~2047	0.0879°	Calibration expressed range: -2047~2047; write 4 to fault reset (134) to auto-compute the centre position (2048); the calibration value is then stored to this address
16	0x10	40017	Operating mode	2	0	R/W	0~4	None	0: servo mode 1: constant-speed mode 2: reserved 3: special mode (torque is switched off automatically when the goal position is reached) 4: stepper mode
17	0x11	40018	Position closed-loop P coefficient	2	–	R/W	0~254	None	Controls the proportional coefficient of the motor
18	0x12	40019	Position closed-loop D coefficient	2	–	R/W	0~254	None	Controls the derivative coefficient of the motor
19	0x13	40020	Position closed-loop I coefficient	2	0	R/W	0~254	None	Controls the integral coefficient of the motor
20	0x14	40021	Velocity loop P coefficient	2	–	R/W	0~254	None	Speed-loop proportional coefficient in constant-speed motor mode (mode 1)
21	0x15	40022	Velocity loop I coefficient	2	–	R/W	0~254	None	Speed-loop integral coefficient in constant-speed motor mode (mode 1)

2.3 SRAM Control¶

Address (DEC)	Address (HEX)	Address (PLC)	Function	Bytes	Initial value	Access	Range	Unit	Description
128	0x80	40129	Goal position	2	0	R/W	-32768~32767	0.0879°	Absolute position control; the maximum corresponds to the maximum effective angle
129	0x81	40130	Torque switch	2	0	R/W	0~1	None	Write 0: torque output off; write 1: torque output on
130	0x82	40131	Acceleration	2	Acceleration default value	R/W	0~65535	8.79°/s²	If set to 0 the servo accelerates at its maximum acceleration; assigned at power-on from the "acceleration default value (405)"
131	0x83	40132	Running speed	2	Speed default value	R/W	0~65535	0.732RPM	Assigned at power-on from the "speed default value (406)"
132	0x84	40133	Torque limit	2	Torque limit default value	R/W	0~1000	0.1%	The initial value is assigned at power-on from the torque limit default value (0x194); you can modify it to control the maximum torque output. Note that changing this torque limit also affects the rotation speed, reducing the maximum no-load speed proportionally
133	0x85	40134	Lock flag	2	1	R/W	0~1/128	None	Write 0 to close the EPROM write lock: values written to EPROM addresses persist after power-off; write 1 to open the write lock: values written to EPROM addresses do not persist; write 128 to close the factory-parameter write lock
134	0x86	40135	Fault reset	2	0	R/W	0~65535	None	Setting the corresponding bit to 1 resets that fault; on success the corresponding bit is cleared; see Special Byte Explanation for details

2.4 SRAM Feedback¶

Address (DEC)	Address (HEX)	Address (PLC)	Function	Bytes	Access	Range	Unit	Description
256	0x100	40257	Servo status	2	R	–	None	A bit set to 1 indicates the corresponding error; see Special Byte Explanation for details
257	0x101	40258	Present position	2	R	–	0.0879°	Feedback of the present position; in absolute position control the maximum corresponds to the maximum effective angle
258	0x102	40259	Present speed	2	R	–	0.732RPM	Rotational speed feedback of the motor
259	0x103	40260	Output PWM	2	R	–	0.1%	Duty cycle of the output driving the motor
260	0x104	40261	Present voltage	2	R	–	0.1V	Current working voltage of the servo
261	0x105	40262	Present temperature	2	R	–	°C	Current internal working temperature of the servo
262	0x106	40263	Moving flag	2	R	–	None	1 while the servo is moving, 0 when the goal is reached and the servo stops
263	0x107	40264	Present current	2	R	–	6.5mA	Maximum measurable current is 500 * 6.5mA = 3250mA

2.5 Factory Parameters¶

Address (DEC)	Address (HEX)	Address (PLC)	Function	Bytes	Initial value	Access	Range	Unit	Description
384	0x180	40385	Moving detection threshold	2	–	Default	–	None	Servo factory default parameter
385	0x181	40386	D control time	2	–	Default	–	None	Servo factory default parameter
386	0x182	40387	Maximum speed limit	2	–	Default	0~32767	0.732RPM	Servo factory default parameter
387	0x183	40388	H-bridge dead time	2	–	Default			Servo factory default parameter
388	0x184	40389	Acceleration limit	2	–	Default	0~65535	8.79°/s²	Servo factory default parameter
389	0x185	40390	Startup torque	2	–	Default	0~1000	0.1%	Sets the minimum output startup torque of the servo; 1000 = 100% * stall torque
390	0x186	40391	Clockwise deadband	2	–	Default	0~32	0.0879°
391	0x187	40392	Counter-clockwise deadband	2	–	Default	0~32	0.0879°
392	0x188	40393	Phase	2	–	Default	0~255	None	Special function byte; do not modify unless specifically required, see Special Byte Explanation for details
393	0x189	40394	Protection switch	2	–	Default	0~255	None	Set a bit to 1 to enable the corresponding protection, set it to 0 to disable it; see Special Byte Explanation for details
394	0x18A	40395	LED alarm condition	2	–	Default	0~255	None	Set a bit to 1 to enable the flashing alarm, set it to 0 to disable it; see Special Byte Explanation for details
395	0x18B	40396	Maximum temperature limit	2	–	Default	0~100	°C	Maximum working temperature limit; if set to 70 the maximum temperature is 70 °C; the setting resolution is 1 °C
396	0x18C	40397	Maximum input voltage	2	–	Default	Minimum input voltage~360	0.1V	If set to 80 the maximum working voltage limit is 8.0V; the setting resolution is 0.1V
397	0x18D	40398	Minimum input voltage	2	–	Default	0~Maximum input voltage	0.1V	If set to 40 the minimum working voltage limit is 4.0V; the setting resolution is 0.1V
398	0x18E	40400	Overload current	2	–	Default	0~511	6.5mA	Overload protection current of the servo
399	0x18F	40401	Overcurrent protection time	2	–	Default	0~5000	1ms	Longest working time with the current above the overload current
400	0x190	40402	Protection torque	2	–	Default	0~1000	0.1%	Output torque after entering overload protection; e.g. 200 means 20% of the maximum torque
401	0x191	40403	Overload torque	2	–	Default	0~1000	0.1%	Maximum torque threshold for triggering overload protection; e.g. 800 means 80% of the maximum torque
402	0x192	40404	Overload protection time	2	–	Default	0~5000	1ms	Longest working time with the torque above the overload torque
403	0x193	40405	Angle resolution	2	1	Default	1~128	None	Magnification factor of the sensor's minimum resolution angle; changing it extends the control range
404	0x194	40406	Torque limit default value	2	1000	Default	0~1000	0.1%	Power-on default for the torque limit
405	0x195	40407	Acceleration default value	2	–	Default	0~65535	8.79°/s²	Power-on default for acceleration
406	0x196	40408	Speed default value	2	–	Default	0~32767	0.732RPM	Power-on default for speed

3 Special Byte Explanation¶

3.1 Servo Phase¶

Bit (weight): Description

BIT0 (1): Drive direction phase; (0) forward, (1) reverse
BIT1 (2): Driver bridge mode; (0) brushless, (1) brushed, takes effect after reboot
BIT2 (4): Torque auto switch; (0) auto-on, (1) command-on, firmware >= 20.9
BIT3 (8): Automatic status reset; (0) auto reset, (1) command reset, firmware >= 20.9
BIT4 (16): Angle feedback mode; (0) single-turn angle feedback, (1) full-angle feedback
BIT5 (32): ----
BIT6 (64): PWM frequency, (0) 24kHz, (1) 16kHz
BIT7 (128): Position feedback direction phase, (0) forward, (1) reverse

Note

If multiple bits are set at the same time, the phase value is the sum of the bit values. Example: with an original phase value of 0, if the servo runs in reverse, the phase value is 128+1=129;

3.2 Servo Status¶

Servo status: 0 means normal, 1 means abnormal

Bit (weight): Description

BIT0 (1): Voltage status
BIT1 (2): Magnetic encoder status
BIT2 (4): Temperature status
BIT3 (8): Current status
BIT4 (16): Torque status: 0 means torque off, 1 means torque on
BIT5 (32): Load status

Note

If multiple statuses occur at the same time, the status value is the sum of the bit values. Example: over-voltage/under-voltage together with servo overheating gives a status value of 4+1=5;

3.3 Protection Switch¶

Unload condition: 0 means off, 1 means on

Bit (weight): Description

BIT0 (1): Voltage protection
BIT1 (2): Magnetic encoder protection
BIT2 (4): Overheat protection
BIT3 (8): Overcurrent protection
BIT4 (16): ----
BIT5 (32): Load overload

Note

If multiple bits are set at the same time, the unload condition value is the sum of the bit values. Example: with voltage protection and overheat protection enabled together, the unload condition value is 4+1=5;

3.4 LED Alarm Condition¶

LED alarm condition: 0 means off, 1 means on

Bit (weight): Description

BIT0 (1): Voltage alarm
BIT1 (2): Magnetic encoder alarm
BIT2 (4): Overheat alarm
BIT3 (8): Overcurrent alarm
BIT4 (16): ----
BIT5 (32): Load overload alarm

Note

If multiple bits are set at the same time, the LED alarm condition value is the sum of the bit values. Example: with the voltage alarm and the overheat alarm enabled together, the alarm condition value is 4+1=5;

3.5 Fault Reset¶

Fault reset: 0 means invalid, 1 means reset

Bit (weight): Description

BIT0 (1): Reset overload fault; with auto-reset enabled, reversing the goal and closing the torque switch can reset the fault
BIT1 (2): Reset overcurrent fault; with auto-reset enabled, reversing the goal and closing the torque switch can reset the fault
BIT2 (4): Centre setting, the current position is set to the 2048 centre
BIT3 (8): ----
BIT4 (16): ----
BIT5 (32): Reset over-voltage/under-voltage; once the voltage returns to normal, write 32 to reset the over-voltage/under-voltage status; with auto-reset enabled, the fault resets automatically once the voltage returns to normal
BIT6 (64): Reset overheat status; once the temperature returns to normal, write 64 to reset the overheat status; with auto-reset enabled, the fault resets automatically once the temperature returns to normal
BIT7 (128): Reset magnetic encoder status; once the magnetic encoder is connected normally, write 128 to reset the magnetic encoder status; with auto-reset enabled, the fault resets automatically once the magnetic encoder is connected normally

Note

If multiple bits are set at the same time, the values of reset-overload-fault and reset-overcurrent-fault are summed. Example: resetting the overload fault together with the overcurrent fault gives a reset value of 1+2=3;

Do not reuse addresses across families

Other series may use the same address with a different meaning (for example, HLS addresses 44–45 are goal current, while SMSMB addresses 132–133 are torque limit). Return to Bus Protocol and select the matching memory table.