This chapter provides information about the supported functions for Siemens devices, and how to access these functions.

3.1 Accessing DAS Functions

DAS for Siemens H1 Protocol functions are accessed through the BASEstar Classic device connection management:

• Commands
• Menu system
• Callable services

To use the BASEstar Classic device connection management commands, enter the following command at the DCL prompt ($):

$ BSTAR DCM

For more information about the BASEstar Classic device connection management commands, refer to the BASEstar Classic Command Line Interface User's Guide.

To use the BASEstar Classic device connection management menu system, enter the following command:

$ BSTAR/MENU

For information about the BASEstar Classic device connection management menu system, refer to the BASEstar Classic Menu Interface User's Guide.

For information about the BASEstar Classic device connection management callable services, refer to the BASEstar Classic Application Programming Interface Reference Guide.

3.2 Supported Functions

This section describes the functions that are supported by the DAS for Siemens H1 Protocol. It explains how these operations are performed from the point of view of the host and from the point of view of the programmable controller. The more complex control operations such as upload, download, start, stop, status are explained in greater detail outlining as much as possible the steps involved. Table 3-1 shows the Siemens devices and the functions supported for them.

Table 3-1 Siemens Devices and Supported Functions

Device	Upload	Download	Start	Stop	Read Data	Write Data	Read Status
S115U	X	X	X	X	X	X	X
S135U	X	X	X	X	X	X	X
S150U	X	X	X	X	X	X	X
S155U					X	X
COMPATIBLE 1					X	X

The host and the Siemens programmable controller are interconnected using Ethernet. The basic communications are carried using the first four layers of the ISO/OSI communications reference model. On the host side this is done using DECnet Plus which implements the first four layers. DECnet Plus provides the basic communication environment for data exchange. As such it allows for programs such as DAS for Siemens H1 Protocol to establish Transport connections with the Siemens programmable controller, and then to exchange data packets to transfer information. These data packets are encoded according to the Siemens specific protocol called H1. The DAS for Siemens H1 Protocol implements the H1 protocol to send commands to the programmable controller to obtain data, to understand the meaning of the data, and to make it available to application programs on the host.

For upload or download operations, the application program provides the DAS for Siemens H1 Protocol with the name of a file on the host. The DAS for Siemens H1 Protocol then sends the file to the memory of the programmable controller.

3.2.1 Supported Communications Cards

From the point of view of the programmable controller there are several cards which cooperate to execute the operations. First, there is the CPU and the memory card. Next there is the CP-535 Ethernet communications card which connects the programmable controller to the Ethernet backbone.

For normal read or write operations, the CP-535 exchanges data with the CPU using a special dual-port RAM. Normally this dual-port RAM needs to be synchronized between the CP-535 and the CPU. Please refer to the appropriate Siemens documentation for the required programming steps on the CPU of the programmable controller to do this.

For control operations such as upload, download, status, start and stop, the CPU is sometimes stopped and thus the dual-port RAM is inoperable. In this case, a second communication card is used, the CP-511. This is an RS-232 based communication card which is able to communicate directly with the CPU even when the CPU is stopped.

The CP-535 and the CP-511 cards are interconnected using a special cable. The control operation is sent from the host to the CP-535, the CP-535 sends it to the CP-511 which then forwards the operation to the CPU.

For model S135U programmable controllers, the CP-511 card is not required as the CPU card itself may be connected directly to the CP-535.

Model S135U programmable controller allows for multiple CPU cards within the same programmable controller. To coordinate between the CPUs, there is a special Coordinator/MUX card. In this configuration, read and write operations are done as before using the dual-port RAM and data is exchanged with the host as before.

For control operations, the special RS-232 cable must be connected between the CP-535 and any of the CPUs or between the CP-535 and the Coordinator. When the cable is connected directly to the CPU, the programmable controller appears to the host as a uniprocessor programmable controller. When the special RS-232 cable is connected to the Coordinator card, then control operations may be performed to any of the CPUs. Thus it is not necessary to move the cable from one CPU to the other to upload the contents of any CPUs in the programmable controller.

In the case uploads may be performed remotely without having to move the cable between the CP-535 and each of the CPUs in the programmable controller.

3.2.2 TSAPs, Establishing Communications

The transport service provides transport users with the means to set up, transfer data across and conclude transport connections. The transport connection is a two-way data transfer path between two transport users. On the programmable controller side the transport user is the CP-535 communication card. On the host side the transport user is the DAS for Siemens H1 Protocol. Each transport user is associated with a TSAP.

Application programs do not need to have separate TSAPs. They do not establish a transport connection directly to the programmable controller. They all use the transport connection established between the programmable controller and the DAS for Siemens H1 Protocol.

The number of available TSAPs is a limited resource both on the host and especially on the programmable controller. Therefore, all application programs on the same host use only one channel.

The name of the TSAP on the host is fixed by default as VAXVAXVA .

The host may connect with up to three TSAPs on the programmable controller. Available TSAPs are the read, write, and unsolicited TSAPs. The read TSAP is used to read data from the programmable controller. The write TSAP is used to write data to the programmable controller. The unsolicited TSAP is used to send or receive data packets.

In addition to these there is a fixed command TSAP on the programmable controller which is used for control operations such as upload, download, start, stop and status.

The name of this command TSAP is fixed by default as S5PGCONN .

There can only be one connection at a time to this special TSAP. The programmable controller allows only one user or application program at a time to do upload, download, status, etc.

All the TSAPs names are configurable. On the host this is specified as part of the /NETADDR qualifier of the device definition. See Device address format for further information.