Colour Display System SEMIGRAF 240 - The history of Ericsson

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90 Fig. 8 Keyboard for SEMIGRAF 240 with individual power feeding. The communication with the control unit is carried outin series form via opto-insulated current sections. There are built-in circuits for acoustic alarm (bell). The read/write memory for character storage enables characters with arbitrary shapes, within the limits of the character matrix, to be programmed in from a main computer or from the keyboard. Characters stored in the read/write memory are lost when the voltage to the control unit is switched off, and must be programmed in again when starting up. The building up of new characters for a user-oriented character range is simplified by the built-in interactive routine for creating new characters with the aid of the keyboard. When a new character is to be built up this routine is started by depressing a key on the keyboard. A frame is then displayed on the screen, within which the character is shown magnified during the building-up process. A cursor can then be moved within the frame and each point in the character matrix can be specified as foreground or background. When the character matrix has been built up as desired, the character can be stored in the character store under the desired name. The programmed character can then be written on the screen and thereby checked that it is correct. If the operator is not satisfied with a certain character it can be returned to the programming frame, cor rected and then finally stored again. A set of characters that has been built up in this way can be read into the main computer by means of a special command and stored there in a bulk store. When the system is started up, or when a new set of characters is required, the character store can then be loaded with the desired set. Keyboard The keyboard for SEMIGRAF 240 has been specially designed so that it can be placed a long way away from the control unit. The keyboard has its own power supply and when installed is connected to the nearest wall socket. Communication between the keyboard and the control unit takes place via a cable with four conductors. The character codes have a length of 8 bits and are sent from the keyboard in series form at a signalling speed of 300 Baud. The keyboard contains a locking key with which the operator can signal to the control unit when it is to be on-line. The keyboard also contains a bell which can be activated from the control unit. All communication to and from the keyboard takes place with current loops of 20 mA.
Fig. 9, left The control unit consists of a 19 printed board unit with built-in power supply Fig. 10 The processor board, CPU, is a complete eight-bit computer with central processing unit, program store, data store, vectorial break logic and two interfaces in series Communication with a main computer The control unit can communicate with a main computer in parallel or series form. The standard version has a series channel in accordance with CCITT V24 in full duplex and the transmission speed is switchable between 110 and 9600 Baud. The transmission is carried out either with or without parity check. Transmission with parity check is carried out in blocks with a maximum length of 128 bytes, each block starting with STX and finishing with ETX. Any type of parallel connection may be used, the choice depending only on the type of computer to which the control unit is to be connected. Division into hardware and software The functions of the control unit can be divided into two groups: a. the control of the colour monitor, which is tied to the timing sequence b. other functions. The direct drawing of the picture on the colour monitor is a fast process that must be repeated regularly in order to maintain the picture on the screen. All the direct picture drawing on the screen is implemented in hardware. The 8-bit microprocessor included in the control unit is quite unable to operate at the speeds required to carry out the direct picture drawing, since each raster point in a picture has a time dimension of only about 100 nanoseconds. The tasks of the processor are: — to handle the communication with a main computer via the computer input and output devices — to handle the communication with the keyboard via the keyboard input and output devices — to interpret the character sequences received from keyboard and computer and to carry out the requested functions — to write in external information in the picture store — to write in the character store — to move information in the picture store (editing) — to fetch information from the picture store or character store and send it to the main computer (e.g. "read line"). Many functions are thus carried out or controlled by software, which gives a unit that can easily be adapted to special application requirements. It has also been possible to adapt the system to the users — human beings — and at the same timeto arrange efficient means of communication with a main computer.
Page 1: ERICSSON REVIEW 3 1978 COLOUR DISPL
Page 4 and 5: Colour Display System SEMIGRAF 240
Page 6 and 7: 88 Fig. 4 The three beams red, gree
Page 10 and 11: Operational Experience of ANA 30 in
Page 12 and 13: 94 Fig. 3 Changing subscriber categ
Page 14 and 15: New Generation of 120 and 480-Chann
Page 16 and 17: 98 Fig. 3 Translation of basic supe
Page 18 and 19: 100 Fig. 6 Line terminating shelf s
Page 20 and 21: Fig. 10 Branching for direct termin
Page 22 and 23: Fig. 16 Housing for one line repeat
Page 24 and 25: AXB 20 - Operation and Maintenance
Page 26 and 27: Fig. 4 Display terminal connected t
Page 28 and 29: 110 Fig. 8 Procedure for changing d
Page 30 and 31: System data for AXB 20 Application
Page 32: TELEFONAKTIEBOLAGETLM ERICSSON ISSN

Colour Display System SEMIGRAF 240 - The history of Ericsson

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