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S7-200 Transmit andReceive (Freeport onRS485 / RS232)S7-200 SMART c/pages/default.aspxSiemensIndustryOnlineSupport

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Table of contentsTable of contentsWarranty and liability . 21Introduction . 41.11.22Engineering . 52.13Hardware setup . 5Engineering . 63.13.23.34Overview. 4Components used . 4Description of interface. 6Project integration . 6Operation . 17Appendix . 18Service and support . 18Application support . 19Links and literature . 19Change documentation . 19 Siemens AG 2019 All rights reserved4.14.24.34.4S7 –200 Smart FreeportEntry-ID: 5, V0.0, 07/20193

1 Introduction1Introduction1.1OverviewUser can use the Transmit (XMT) and Receive (RCV) instructions forcommunication between a S7‑200 SMART CPU and other devices or S7-200SMART through the CPU serial port(s). Each S7‑200 SMART CPU provides anintegrated RS485 port (Port 0). The standard CPUs additionally support an optionalCM01 Signal Board (SB) RS232/RS485 port (Port 1). The communication protocolmust be implemented in the user program.User can select the Freeport mode to control the serial communications portof the CPU by means of your user program. When user select Freeport mode,program controls the operation of the communications port through the use of thereceive interrupts, the transmit interrupts, the Transmit instruction, and the Receiveinstruction and entirely controls the communications protocol while in Freeport mode.1.2Components used Siemens AG 2019 All rights reservedThis application example has been created with the following hardware and softwarecomponents:Table 1-1ComponentNumberArticle numberCPU ST3026ES7288-1ST30-0AA0STEP 7-MicroWINSMART V2.316ES7-288S-W01-0AA0Ethernet Switch1-NoteFirmware Ver. 2.3This application example consists of the following components:Table 1-2ComponentFile nameS7-200 Smart FreeportTransmit and Receive1) PLC 1 (1st transmit then receive).smart2) PLC 2 (1st receive then transmit).smartS7 –200 Smart FreeportEntry-ID: 5, V0.0, 07/2019Note4

2 Engineering2Engineering2.1Hardware setup: Siemens AG 2019 All rights reservedThe figure below shows a schematic overview of the most important components of thesolution:S7 –200 Smart FreeportEntry-ID: 5, V0.0, 07/20195

3 Engineering3Engineering3.1Description of instructions Siemens AG 2019 All rights reservedLAD / FBDSTLDescriptionXMT TBL, PORTThe Transmit instruction(XMT) is used in Freeportmode to transmit data bymeans of the communicationsport(s).RCV TBL, PORTThe Receive instruction (RCV)initiates or terminates thereceive message function.User must specify a start andan end condition for thereceive box to operate.Messages received throughthe specified port (PORT) arestored in the data buffer (TBL).The first entry in the databuffer specifies the number ofbytes received.Input / outputData typeOperandTBLBYTEIB, QB, VB, MB, SMB, SB, *VD, *LD, *ACPORTBYTEConstant: 0 or 1Note: The two available ports are as follows: Integrated RS485 port (Port 0), CM01 Signal Board (SB) RS232/RS485 port(Port 1)You can select the Freeport mode to control the serial communications port ofthe CPU by means of your user program. When you select Freeport mode, yourprogram controls the operation of the communications port through the use of thereceive interrupts, the transmit interrupts, the Transmit instruction, and the Receiveinstruction and entirely controls the communications protocol while in Freeport mode.You use SMB30 and SMB130 to select the baud rate and parity.The CPU assigns two special memory bytes to the two physical ports:1) SMB30 to the integrated RS485 port (Port 0)2) SMB130 to the CM01 RS232/RS485 Signal Board (SB) port (Port 1)The Freeport mode is disabled and normal communications are reestablished (for example, HMI device access) when the CPU is in STOP mode.In the simplest case, User can send a message to a printer or a display usingonly the Transmit (XMT) instruction. Other examples include a connection to a barcode reader, a weigh scale, and a welder. In each case, user must write program toS7 –200 Smart FreeportEntry-ID: 5, V0.0, 07/20196

3 Engineeringsupport the protocol that is used by the device with which the CPU communicateswhile in Freeport mode.User can only use Freeport communications when the CPU is in RUN mode.Enable the Freeport mode by setting a value of 01 in the protocol select field ofSMB30 (Port 0) or SMB130 (Port 1). While in Freeport mode, it cannot communicatewith an HMI on the same port.3.2Project integration1. Changing PPI communications to Freeport mode. Siemens AG 2019 All rights reservedSMB30 and SMB130 configure the communications ports, 0 and 1 respectively,for Freeport operation and provide selection of baud rate, parity, and number of databits. The following figure describes the Freeport control byte. One stop bit isgenerated for all configurations.ppbbbParity select00 No parity01 Even parity10 No parity11 Odd parityFreeport baud rate000 38400001 19200010 9600011 4800100 2400101 1200110 115200111 57600dData bits per character0 8 bits per character1 7 bits per charactermmProtocol selection00 PPI slave mode01 Freeport mode10 Reserved (defaults to PPI slave mode)11 Reserved (defaults to PPI slave mode)2. Transmit data.The Transmit instruction lets you send a buffer of one or more characters, up to amaximum of 255. The following figure shows the format of the Transmit buffer.① Number of bytes to transmit② Characters of the messageIf an interrupt routine is attached to the transmit complete event, the CPUgenerates an interrupt (interrupt event 9 for port 0 and interrupt event 26 for port 1)after the last character of the buffer is sent.S7 –200 Smart FreeportEntry-ID: 5, V0.0, 07/20197