Browse Prior Art Database

Table Driven Programmable Adapters

IP.com Disclosure Number: IPCOM000087397D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

VanderGoor, AJ: AUTHOR

Abstract

In an intelligent terminal system the available main processor and microprogram facilities are used for microprogram control of the hardware functions of stepping motors, wire printers, drum printers and the like, resulting in extremely flexible hardware control as well as simplified hardware adapter design.

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Table Driven Programmable Adapters

In an intelligent terminal system the available main processor and microprogram facilities are used for microprogram control of the hardware functions of stepping motors, wire printers, drum printers and the like, resulting in extremely flexible hardware control as well as simplified hardware adapter design.

Fig. 1 shows the general flow diagram of a microprogrammed adapter system. A command for a hardware device, normally triggering a sequence of specific hardware operation steps, is compiled by the main processor of the terminal into a microprogram using a special instruction set, which is stored in memory. The adapter sequentially fetches the microinstructions from memory via the main processor by means of cycle stealing techniques and supplies them to a special purpose processor, i.e., the hardware adapter. Each microinstruction controls one or more predetermined hardware functions, including the timing of these functions. The adapter decodes the straightforward linear-programmed microinstruction sequence into hardware control of the device involved.

All hardware functions, such as paper feed, printing, ribbon selection, timing etc. are controlled by these microinstructions, while general parameter functions, such as the layout of the characters on a printing drum surface, the layout of wire printer characters, the timing pulse sequence of a stepping motor and the like, are combined in easily changeable tables in memory, enhancing the flexibility of the system.

Figs. 2-4 show the microprogram adapter system as applied to a drum printer. The rotating cylinder of a drum printer comprises lines of character profiles on its surface, which are successively opposed to a row of hammers at the print positions of a line. In one revolution of the drum all the characters pass under their associated hammers, and by appropriate selection of the hammer firing times, a complete line is printed during one drum revolution.

For this drum printer the general flow diagram of Fig. 1 has the more specific form of Fig. 2. Normally each print command is accompanied by an EBCDIC character string to be printed on one line. Each print command is compiled into a printer microprogram, consisting of a succession of entries, as specified in Fig. 3. Each entry corresponds to one or more microinstructions, controlling one specific hardware function. A single print command may therefore be compiled into the complete string of entries, shown in Fig. 3, and control in succession motor operation, paper feed, ribbon selection and printing of a line. Depending on the command involved and the state of the device, the string of...