MODBUS Slave Protocol: Difference between revisions

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* read/write
* read/write
* values range 0x0001... 0xFFFF
* values range 0x0001... 0xFFFF

Revision as of 14:23, 27 June 2025

Smart LCD MODBUS Salve Product can be accessed by MODBUS Master devices for real-time control and access.

Basic

MODBUS Communication

The MODBUS is a standard protocol (with RTU or ASCII mode) which is used to communicate between a host and one or multiple slave devices. Over the MODBUS the host is able to communicate with up to 254 slaves. It can read or write data areas on these devices.

The SMART LCD Slave Product works as a slave device in RTU mode. Therefore, we only describe the RTU mode within this document. 

General MODBUS Frame consists:
- 1byte of Device Address, to indicate which slave device shall response
- 1byte of Function Code, to tell the addressed slave which function is going to do
- Data content for PAGE, Addresses and data values
- 2-Byte CRC for Error Checking
< - - - - - - - - - - - - - - - - - - - - - - - - - ADU - - - - - - - - - - - - - - - - - - - - - - - - - > 
Device Address (1byte)

Function Code (1byte)

Data (252bytes(max.))

Error Check (2bytes)
< - - - - - - - - - - PDU - - - - - - - - - - >

When the host receives the previous frame reply from the slave device, the host needs an interval of 5ms before it can continue to send the next frame command. Since the SMART LCD is a Modbus slave device, a Device Address must be assigned to it. Device address can be assigned in the TOPWAY’s SGTools.

MODBUS Function Codes

MODBUS Function Code Function Definition Address Range Object Type
0x03 Read Multiple Holding Registers 0x0000 ~ 0xFFFF 2 Bytes
0x06 Write Single Holding Register 0x0000 ~ 0xFFFF 2 Bytes
0x10 Write Multiple Holding Registers 0x0000 ~ 0xFFFF 2 Bytes
0x11 Report Slave ID
0x14 Read File Record 1 File with 2048 Records of 128 Byte

MODUBS Address and Mapping with Smart LCD

To access memory locations in the SMART LCD the host has to issue a Read or Write function, which includes a specific address. Each Read or Write function accesses a 2-Byte location within an area of up to 64k words. Since the multiple data areas (N16, N32, N64, etc.) are together larger than 64k Words, the different memory areas are separated into pages. To select a specific page the Modbus Page Map Register must be written with the page number. The Page Map Register is located within the set of Special Function Registers. The Special Function Registers (SFR) are accessible on all pages at the same location. They are placed within the final 4k words of all pages.

In SGTools, MENU --> View --> Show Modbus Holding Register Address can show up the VPs corresponding MODBUS ADDRESS for the display UI.

Relationship between MODBUS PAGE:addresses and the SMART LCD VPs

VP type SMART LCD VP Address MODBUS PAGE: Address note
VP_STR 0x000000, 0x000080 - 0x01DF80 0:0x0000, 0:0x0040 - 0:0xEFC0
VP_N32 0x020000, 0x020004 - 0x02FFDC 1:0x0000, 1:0x0002 - 1:0x7FEE
TIMER COUNTER 0x02FFE0, 0x02FFE4 - 0x02FFFC 1:0x7FF0, 1:0x7FF2 - 1:0x7FFE Timer 0, Timer 1 - Timer 7
VP_N64 0x030000, 0x030008 - 0x03FFF8 6:0x0000, 6:0x0004 - 6:0x7FFC
VP_N16 0x080000, 0x080002 - 0x08FFFE 4:0x0000 - 4:0x7FFF
VP_BMP 0x040000 - 0x05DFFE 2:0x0000 - 2:0xEFFF
VP_G16 0x060000 - 0x06EFFF 3:0x0000 - 3:0xEFFF
VP_Flash 120kB Flash memory 5:0x0000 - 5:0xEFFF remain unchanged even after power down
VP_REG 0xFFF000 - 0xFFFFFF -- VP_Reg can not be accessed directly via MODBUS
SFR -- n:0xF000 - n:0xFFFF SFR for Smart LCD MODBUS PAGE and some of the VP_REG functions

MODBUS Function Codes Details

The SMART LCD supports five MODBUS Functions Codes: 0x03, 0x06, 0x10, 0x11, 0x14

Function Code 0x03 - “Read Multiple Holding Registers”

This function code read up to 250 Bytes from the SMART LCD.

Host to Smart LCD MODBUS Frame

Byte Seq Content No. of Byte Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x03
2 Start Address to be read 2 0x0000 … 0xFFFF Address location that MODBUS PAGE assigned via SFR
4 Quantity of data 2 0x0001 … 0x007D no. of 16 Bit data values to be read
6 CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x03
4 Byte Count N 1 0x02 … 0xFA must be an even number, must be double of the requested "Quantity of data" in16 Bit values
6 N Bytes of data N 0x00 … 0xFF
6 + N CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host (in case of error found)

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Error Code 1 0x83
2 Exception Code 1 0x01 ... 0x04 01=Illegal Functrion; 02=IllegalDataAddress; 03=IllegalDataValue; 04=SlaveDeviceFailure
3 CRC 2 0x0000 … 0xFFFF for error checking

Example Frame (Read a VP_N32 value form Smart LCD (device address = 01))

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F0 01 00 01 2A CA Set the Smart LCD MODBUS PAGE =1; omit this frame for continue access the same PAGE
2 RX 01 06 F0 01 00 01 2A CA
3 TX 01 03 00 00 00 02 C4 0B Read multiple data form address 00 00, and get 00 02 16bit values
4 RX 01 03 04 33 44 11 22 39 2B no. of byte =04; Data value = 0x11223344

Function Code 0x06 - “Write Single Holding Register”

This function code write 2 Bytes to the SMART LCD.

Host send to Smart LCD MODBUS frame

Byte Seq Content No. of Byte Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7 0x00 is a broadcast message to all devices
1 Function Code 1 0x06
2 Address to be writen 2 0x0000 … 0xFFFF Address location that MODBUS PAGE assigned via SFR
4 Data value 2 0x0001 … 0x007D 16 Bit data values to be written
6 CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x06
2 Address wrote 1 0x02 … 0xFA must be an even number, must be double of the requested "Quantity of data" in16 Bit values
4 Data value 2 0x0001 … 0x007D 16 Bit data value wrote
6 CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host (in case of error found)

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Error Code 1 0x86
2 Exception Code 1 0x01 ... 0x04 01=Illegal Functrion; 02=IllegalDataAddress; 03=IllegalDataValue; 04=SlaveDeviceFailure
3 CRC 2 0x0000 … 0xFFFF for error checking

Example Frame (Write a VP_N16 value to Smart LCD (device address = 01))

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F0 01 00 04 EA C9 Set the Smart LCD MODBUS PAGE =4; omit this frame for continue access the same PAGE
2 RX 01 06 F0 01 00 04 EA C9
3 TX 01 06 00 00 12 34 84 BD Write a data 12 34 to address 00 00
4 RX 01 06 00 00 12 34 84 BD

TX=host to Smart LCD; RX=Smart LCD reply to host

Function Code 0x10 - “Write Multiple Holding Registers”

This function code write up to 246 Bytes to the SMART LCD.

Host send to Smart LCD MODBUS frame

Byte Seq Content No. of Byte Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7 0x00 is a broadcast message to all devices
1 Function Code 1 0x10
2 Start Address to be write 2 0x0000 … 0xFFFF Address location that MODBUS PAGE assigned via SFR
4 Quantity of data (Q) 2 0x0001 … 0x007B no. of 16 Bit data values to be written
6 Byte Count 1 0x02 … 0xF6 must be an even number and exactly the double of Q
7 Data to be written 2 x Q 0x0000 ... 0xFFFF
7 + Q CRC 2 0x0000 ... 0xFFFF for error checking

SMART LCD reply to host

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x10
2 Start Address wrote 2 0x0000 … 0xFFFF Address location that MODBUS PAGE assigned via SFR
4 Quantity of data worte 2 0x0001 … 0x007B no. of 16 Bit data values wrote
6 CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host (in case of error found)

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Error Code 1 0x90
2 Exception Code 1 0x01 ... 0x04 01=Illegal Functrion; 02=IllegalDataAddress; 03=IllegalDataValue; 04=SlaveDeviceFailure
3 CRC 2 0x0000 … 0xFFFF for error checking

Example Frame (Write two VP_N16 value to Smart LCD (device address = 01))

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F0 01 00 04 EA C9 Set the Smart LCD MODBUS PAGE =4; omit this frame for continue access the same PAGE
2 RX 01 06 F0 01 00 04 EA C9
3 TX 01 10 00 00 00 02 04 56 78 12 34 06 68 Write two 16bit data 12 34 and 56 78 to address 00 00
4 RX 01 10 00 00 00 02 41 C8

TX=host to Smart LCD; RX=Smart LCD reply to host

Function Code 0x11 - "Report Slave ID"

This function code allows the host to check some slave device information like device name and revision. Additional there is one byte indicating the current operational status of the slave device, called the Run Indicator Status. The SMART LCD will always set this byte to 0xFF (Powered On)

Host send to Smart LCD MODBUS frame

Byte Seq Content No. of Byte Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x11
2 CRC 2 0x0000 ... 0xFFFF for error checking

SMART LCD reply to host

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x11
2 Byte Count 1 0x01 ... 0xF9 byte count of all the following data except CRC
3 Slave ID n 0x00 ... 0xFF in ASCII (e.g. SMART LCD V1.03)
3 + n Run Indicator Status 1 0xFF 0xFF for Powered On
3 + n + 1 CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host (in case of error found)

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Error Code 1 0x91
2 Exception Code 1 0x01, 0x04 01=Illegal Functrion; 04=SlaveDeviceFailure
3 CRC 2 0x0000 … 0xFFFF for error checking

Example Frame (Ask for Slave ID of Smart LCD (device id = 01))

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 11 C0 2C
2 RX 01 11 11 48 4D 54 30 37 30 43 4E 2D 43 20 56 31 2E 30 33 FF 29 30 Slave ID is “SMART LCD V1.03”

TX=host to Smart LCD; RX=Smart LCD reply to host

Function Code 0x14 - "Read File Record"

This function code allows the host to read up to 128 Byte of a special file (USR.BIN) at once. The file USR.BIN may be placed together with the TML project data into the file system of the SMART LCD and it may contain any additional data used by the host. The file size of USR.BIN may be up to 256k Byte. It is organized into 2048 records. Each record consists of 128 Bytes.

Host send to Smart LCD MODBUS frame

Byte Seq Content No. of Byte Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x14
2 Byte Count 1 0x07 byte count of all the following data except CRC
3 Reference Type 1 0x06
4 File Number 2 0x0001
6 Record Number 2 0x0000 ... 0x07FF Record Number of a one of the 2048 possible records within USR.BIN
8 Record Number 2 0x0001 ... 0x003F Record Number of a one of the 2048 possible records within USR.BIN
10 CRC 2 0x0000 ... 0xFFFF for error checking

SMART LCD reply to host

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Function Code 1 0x14
2 Reply Byte Count 1 0x04 ... 0x82 byte count of all the following data except CRC
3 Record Byte Count n 0x03 ... 0x81 byte count of all the following data except CRC
4 Reference Type 1 0x06 0xFF for Powered On
5 Data 2 x n 0x00 ... 0xFF read from record with N 16 Bit words ranging from 1 to 64.
5 + (2xN) CRC 2 0x0000 … 0xFFFF for error checking

SMART LCD reply to host (in case of error found)

Byte Seq Content Byte Count Valid Range note
0 MODBUS Device Address 1 0x01 … 0xF7
1 Error Code 1 0x94
2 Exception Code 1 0x01 ... 0x04 01=Illegal Functrion; 02=IllegalDataAddress; 03=IllegalDataValue; 04=SlaveDeviceFailure
3 CRC 2 0x0000 … 0xFFFF for error checking

Example Frame (Read File Record (device id = 01))

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 14 07 06 00 01 00 00 00 01 05 24 read record file 00 01, record 00 00 and one 16bit value
2 RX 01 14 04 03 06 02 01 D9 F1 two bytes read back are 0x01, 0x02.

TX=host to Smart LCD; RX=Smart LCD reply to host

Since the Modbus protocol organizes data in 16 Bit words the file size of USR.BIN should be even. In case the file size is uneven the SMART LCD would pad the last data word with an additional 0x00.

Modbus Error Codes Details

In case the SMART LCD receives a command with invalid data, invalid data count or an unsupported function code it will return an error code to the host (Returning the same function code with an additional Bit7 set). Additional it will transfer one of four possible exemption codes to indicate to the host what kind of error occurred

Code Exemption Name Descriptions
0x01 ILLEGAL FUNCTION The function code is not supported by the SMART LCD
0x02 ILLEGAL DATA ADDRESS The data address by the SMART LCD falls into a undefined area.
0x03 ILLEGAL DATA VALUE A data value received by the SMART LCD is not valid. It does not fit to the specific range requirements for the particular address.
0x04 SLAVE DEVICE FAILURE An unrecoverable error occurred while the SMART LCD was attempting to perform the requested action.

Color and Data Value Configuration

To access data the host should do following steps using the Modbus protocol:

  1. Use “Write Single Holding Register” with function code (0x06) to address 0xF001 and the data value of the desired memory page (0x01 … 0x05)
  2. Write to or read from the desired address within the selected page with: “Read Multiple Holding Registers” with function code (0x03) “Write Single Holding Register” with function code (0x06) "Write Multiple Holding Registers” with function code (0x10)

Each Modbus address holds 16 Bit of data. Therefore, it might be necessary to read multiple address locations:

  • STR, up to 64 consecutive accesses might be necessary to read an entire string, One single access will manipulate two characters.
  • N16, just one access is necessary to access one N16 variable. Multiple N16 variables might be accessed with a single Modbus command.
  • N32, two accesses are necessary to access one N32 variable. Multiple N32 variables might be accessed with a single Modbus command.
  • N64, four accesses are necessary to access one N64 variable. Multiple N64 variables might be accessed with a single Modbus command.
  • Bitmap, one access can manipulate 16 pixels of a bitmap variable. Multiple pixels might be accessed with a single Modbus command.
  • Graph, one access can manipulate one data point of a graph. Multiple data points might be accessed with a single Modbus command.

“Read Multiple Holding Registers” with function code (0x03) allows accessing of up to 125 consecutive address locations at once, with each location holding two Bytes of data.

“Write Multiple Holding Registers” with function code (0x10) allows accessing of up to 123 consecutive address locations at once, with each location holding two Bytes of data.

Access to the Special Function Registers, which are mapped to all pages, should not exceed the required Byte count assigned to each SFR. In such a case the SMART LCD would reply the host with an error message.

Note: Since the Modbus protocol uses a “Big-Endian” representation of data, the first Byte of each 16 Bit word represents the upper 8 Bit of the data word. In contrary the memory organization of the SMART LCD is “Little-Endian” requiring the host to swap upper and lower Byte of each transaction.

16 bit color value
R4 R3 R2 R1 R0 G5 G4 G3 G2 G1 G0 B4 B3 B2 B1 B0
High byte (MSB) Low byte (LSB)
D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
64bit number value
D63...D56 D55...D48 D47...D40 D39...D32 D31...D24 D23...D16 D15...D8 D7...D0
Byte7 (MSB) Byte0 (LSB)
D7...D0 D7...D0 D7...D0 D7...D0 D7...D0 D7...D0 D7...D0 D7...D0
32bit number value
D31...D24 D23...D16 D15...D8 D7...D0
Byte3 (MSB) Byte0 (LSB)
D7...D0 D7...D0 D7...D0 D7...D0
16bit number value
D15...D8 D7...D0
High Byte (MSB) Low Byte (LSB)
D7...D0 D7...D0
String value
D7...D0 D7...D0
Strings are stored Byte by Byte starting from the lower address.

The terminator (0x00) is placed at the highest address. The start address of a string is always even and aligned to a 128 Byte boundary.

Special Function Registers (SFR)

SFR Types

The SMART LCD provides a set of SFR, which allow the host to:

  • Select a Memory Page to be able to access different kinds of VPs
  • Issue graphical drawing commands (Draw Pixels, Lines, Rectangles)
  • Show text or specific icons on the GUI
  • Read or change current page shown on the GUI  
  • Set the Type
  • Control Buzzer, Backlight and Screensaver
  • Read and Set the Real Time Clock (RTC)
  • Select a GUI project (if multiple GUI projects are present)
  • Restart a GUI project
  • Unlock the File System for access via USB
  • Format the File System
  • Change the RS485 communication Baud Rate
  • Start a System Self-Test or the Touch Panel Calibration Routine
SFR Type Descriptions
Command SFR When written with a command code, it may trigger a special command using the values stored in one or multiple other SFRs
MODBUS PAGE SFR When written it will select the specific page. For any subsequent memory access within the Modbus address range of 0x0000 … 0xEFFF.
Graphics SFR For graphical commands issued to the Command Register.
Project Control SFR For GUI project control commands issued to the Command Register
Peripheral Control SFR For commands issued to the Command Register, which control peripheral components of the SMART LCD, such as the Buzzer, the Backlight and the RTC.
Timer Control SFR For commands issued to the Command Register, which control the 8 Timers of the SMART LCD

SFR List

SFR Type SFR Address R/W Size SFR Name Default Value
Command SFR (*1) 0xF000 R/W 2Bytes Command 0x0000 (*2)
MODBUS PAGE SFR 0xF001 R/W 2Bytes Modbus VP Page 0x0004
Project Control SFRs 0xF00A R/W 2 Bytes Project ID 0x0000
0xF200 W 128Bytes USB Password Buffer 0x0000
0xF300 R 4Bytes TP_XY_Position 0x0000
Peripheral Control SFRs 0xF400 R/W 2Bytes Page ID Project Value
0xF401 R 2Bytes Modbus Slave Address Project Value
0xF402 R/W 2Bytes Baud rate Project Value
0xF403 R/W 2Bytes Backlight Level Project Value
0xF404 R/W 2Bytes Screen Saver Backlight Level Project Value
0xF405 R/W 2Bytes Screen Saver Time Project Value
0xF406 R/W 2Bytes Buzzer Key Click Time Project Value
0xF407 R/W 2Bytes cursor type Project Value
0xF408 R/W 6Bytes RTC_NOW in format (YY-MM-DD HH:mm:ss) 0x000101000000 (2000-01-01 00:00:00)
0xF40B R/W 2Bytes Buzzer Sound Time click time
0xF40C R/W 2Bytes Enable Self-Test 0x0000
0xF40D R/W 2Bytes Enable Format 0x0000
0xF40E R/W 2Bytes Enable Touch Panel Calibration 0x0000
System Control SFRs 0xF410 R/W 2Bytes Timer_ctrl 0 0x0000
0xF411 R/W 2Bytes Timer_ctrl 1 0x0000
0xF412 R/W 2Bytes Timer_ctrl 2 0x0000
0xF413 R/W 2Bytes Timer_ctrl 3 0x0000
0xF414 R/W 2Bytes Timer_ctrl 4 0x0000
0xF415 R/W 2Bytes Timer_ctrl 5 0x0000
0xF416 R/W 2Bytes Timer_ctrl 6 0x0000
0xF417 R/W 2Bytes Timer_ctrl 7 0x0000
0xF420 R/W 2Bytes Screen Saver Time1 Project Value
0xF421 R/W 2Bytes Screen Saver Page ID Project Value
0xF422 R/W 2Bytes Codepage Project Value
0xF423 R/W 2Bytes Country code Project Value
0xF424 R/W 2Bytes PinYin EN/CN Switch 0:CN 1: EN
0xF425 R 2Bytes PIP State (1: PIP MODE)
0xF426 R 2Bytes Touch Panel State (1: Press Down; 0: Release)
0xF427 R 2Bytes Touch Key ID 0xFFFF
0xF428 R 2Bytes Current Backlight Level Project Value

note:

*1. The Host may issue a command to Command SFR (address 0xF000). The SMART LCD will interpret the command and execute it.

*2. When 0x0000 read from the Command SFR (address 0xF000) it means that the previous command was executed and the SMART LCD is ready for a next command.

SFR Details

Timers Control SFR

The SMART LCD provide eight 32-Bit timers, which can be used by GUI and host. The timers located within the VP_N32 area. Each Timer has got a Timer Count Register and a corresponding SFR, Timer Control Register for starting, stopping and setting the counting direction of the timers.

All Timers are counting in 1s steps.

n Timer n Control SFR Address Descriptions Timer n MODBUS Address
0 0xF410 Timer Control Registers SFR function code:
  • 0x0000: Timer stop
  • 0x0001: Timer counting down to 0x00000000
  • 0x0003: Timer counting up to 0x7FFFFFFF

note:

Timer0 ~ Timer7 are located in MODBUS PAGE=1

it could be access via UI in VP_N32 area

1:0x7FF0
1 0xF411 1:0x7FF2
2 0xF412 1:0x7FF4
3 0xF413 1:0x7FF6
4 0xF414 1:0x7FF8
5 0xF415 1:0x7FFA
6 0xF416 1:0x7FFC
7 0xF417 1:0x7FFE

Example Frame (device id = 01)

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F4 10 00 03 FA 3E Set the Timer 0 Control SFR of Timer 0 as count up mode
2 RX 01 06 F4 10 00 03 FA 3E
3 TX 01 06 F0 01 00 01 2A CA Select MODBUS PAGE1
4 RX 01 06 F0 01 00 01 2A CA
5 TX 01 03 7F F0 00 02 DD EC Read the Timer 0
6 RX 01 03 04 00 63 00 00 0A 2D Report the Timer register value back to the host

Touch Panel XY Position & State SFRs

The SMART LCD allows the host to read its current touch panel pen position. For this purpose, the host may poll via Modbus the 4 Byte TP_XY_Position Register, which is located in the Special Function Register Area.

SFR SFR Address Descriptions
TP position X 0xF300
  • Read-Only
  • On pen up, the result will be 0xFFFFFFFF
  • On pen down X range will be 0x0000 (left) … 0x031F (right)
TP position Y 0xF301
  • Read-Only
  • On pen up, the result will be 0xFFFFFFFF
  • On pen down Y range will be 0x0000 (up) … 0x01DF (down)
TP State 0xF426
  • Read Only
  • On pen up Status will be 0x0000 (default)
  • On pen down State will be 0x0001

Example Frame (device id = 01)

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 03 F3 00 00 02 F7 4F Read TP position SFR (X&Y)
2 RX 01 03 04 01 7E 01 54 9B B8 Report back to host X=017E; Y=0154

Screen Saver Time1 SFR

The SMART LCD allows the host to modify the screen saver delay time. The register value can be changed under delay 2 in project settings

SFR SFR Address Descriptions
Screen Saver Time1 0xF420
  • read/write
  • values range 0x0001... 0xFFFF
  • SFR value high byte corresponding to system register 0xFFFF25
  • SFR value low byte corresponding to system register 0xFFFF26

Example Frame (device id = 01)

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F4 20 00 05 7A 33 Set the Screen Saver Time to 0005 seconds
2 RX RX: 01 06 F4 20 00 05 7A 33

Screen Saver Page ID Register

The SMART LCD allows the host to change the page ID of the screen saver in run time which normally assigned in the page jump option in project settings.

SFR SFR Address Descriptions
Screen Saver Page JUMP ID 0xF421
  • read/write
  • values range 0x0001... 0x03E7
  • SFR value high byte corresponding to system register 0xFFFF23
  • SFR value low byte corresponding to system register 0xFFFF24

Example Frame (device id = 01)

Seq dir MODBUS Communication Frame Descriptions
1 TX 01 06 F4 21 00 01 2A 30 change the screen saver page jump ID to 0001
2 RX 01 06 F4 21 00 01 2A 30

Command SFR Commands

Command List

Command Code Command Name Descriptions
0x0070 disp_page Display a pre-stored TML file (page)
0x005F backlight_ctrl Set backlight brightness (64 levels)
0x00A0 screen_saver_on Enable Screen Saver
0x00A1 screen_saver_off Disable Screen Saver
0x0079 buzzer_ctrl Set Buzzer Key Click Parameters
0x0080 buzzer_on Sound Buzzer once
0x009C RTC_set Set the RTC
0x00E0 set_baudrate Set RS485 Baud Rate
0x00E1 sel_project Set active project folder
0x00E2 u_drv_format Format File System
0x00E3 u_drv_unlock Unlock File System for USB Access with pre-stored password
0x0088 self_test Starts Self-Test
0x0000 NOP No Operation / No Command to execute

Command Details

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