Contents
© Arcom Control Systems Ltd. 1987 |
Manual | PCB | Comments |
---|---|---|
v1 iss 2 | v1 iss 2 | 1987-02-23 first published in this format |
J069 SVC
The SVC is a video board capable of displaying 80 columns by 25 rows of text. Used in conjunction with a video monitor and serial keyboard the SVC provides an alternative to a text terminal.
Various input devices may be used. For example, serial keyboards can be connected to the CPU board. Details of how to connect a TTL keyboard to an Arcom processor are given in the processor manual. An RS232 keyboard is also available, which avoids re-configuring the serial input/output levels.
The SVC has an on-board dedicated text controller device supporting hardware scroll, non-scrolling 25th row status line, several character attribute modes and an aesthetic 9 by 12 ASCII character set. Interrupts can be generated by the SVC board; this is necessary for character output in "real time" systems.
An attribute (flashing, underlined, half-intensity, graphics, inverse) can be activated in one of two modes. In mode 1, setting bit 7 of a character causes it to display the attribute stored in the Attribute data register, all characters so tagged displaying this same attribute. In mode 2, certain characters are displayed on screen as spaces, but cause the characters following to be displayed with an attribute, which allows several different attributes to be displayed on a screen at once.
Software drivers for the SVC are included with Concurrent DOS, and other operating systems such as CP/M Plus and OS9. These drivers provide partial emulation of Ampex 210 and Televideo 925 text terminals, which is adequate for most wordprocessors and databases. An example driver written in compiled BASIC is shown in Appendix C.
The SVC produces composite video, as well as video with TTL-level horizontal and vertical positive sync. pulses. Field refresh rate is 50 Hz.
J069 SVC
The SVC board with driver software is ideal for use with a development system as an alternative to a text terminal. The emulation software is not capable of full emulation of any particular terminal, however it supports all the following control codes and escape sequences as required for popular software packages such as WORDSTAR and DBASE II. If you have an SVC in your development system, software packages should be installed for a Televideo 925.
The following escape codes are supported by CP/M80 and Concurrent DOS operating systems:
Escape codes hexadecimal Comments values ESC,=, 01BH,03DH, ; Position cursor at row,col (row),(col) (row),(col) ; where (row)=row+020H and ; (col)=column+020H. ESC,T 01BH,054H ; Erase to end of line. ESC,E 01BH,045H ; Scroll screen down at cursor ; and insert blank line. ESC,R 01BH,052H ; Scroll screen up to cursor ; and blank last line. ESC,) 01BH,029H ; Turn on half intensity attribute. ESC,( 01BH,028H ; Turn off half intensity attribute. ESC,f, 01BH,066H, ; Write eighty characters to status line. (80 chars) (80 chars) ; This escape sequence may be ; terminated by a carriage return, 0DH.
A target system can make full use of the SVC's attributes. The attribute character defining one of five attributes can be placed at the beginning and end of a string of characters. The attribute characters are actually displayed as spaces. This attribute mode allows five attributes and simple box drawing graphics to be displayed on the screen at the same time. These features make the SVC especially suited for use with a 5" monitor and touch screen in a target system.