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Addressing Smart Devices by Incrementing and Decrementing the Address Identifier

IP.com Disclosure Number: IPCOM000040642D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Grant, SC: AUTHOR [+2]

Abstract

Most communication addressing of machine control devices (stepping motor controllers, DC servo controllers, etc.) is done by having that device compare an address on the line/bus to a code which is set into on-board digit switches or jumpers. This applies to most interfaces. This approach requires that the user understand the digit-switch coding and must physically set-up its address before it can be operated. The concept is described in the following. Each device is given an address of 0. Each device has four 8-bit parallel communications ports with their own handshake lines - two are input ports and two are output ports. The devices are connected together as shown in Fig. 1. Each device knows that its address is 00H. However, to the host, the address will correspond to the physical location of the device in the line.

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Addressing Smart Devices by Incrementing and Decrementing the Address Identifier

Most communication addressing of machine control devices (stepping motor controllers, DC servo controllers, etc.) is done by having that device compare an address on the line/bus to a code which is set into on-board digit switches or jumpers. This applies to most interfaces. This approach requires that the user understand the digit-switch coding and must physically set-up its address before it can be operated. The concept is described in the following. Each device is given an address of 0. Each device has four 8-bit parallel communications ports with their own handshake lines - two are input ports and two are output ports. The devices are connected together as shown in Fig. 1. Each device knows that its address is 00H. However, to the host, the address will correspond to the physical location of the device in the line. For example, device #1 will have an address of 01H, device #2 will have an address of 02H, etc. An example format of a command is shown in Fig. 2. The last character of the command string is the address identifier. When received, this character is immediately decremented and then compared to 00H. If the character is 00H, the device begins to execute the command and opens up its buffer to more incoming messages for other devices down the line. If the address character is not 00H, the command is immediately sent downstream to the next device where the same operation is p...