GB1395555A - Display terminal controller - Google Patents

Abstract

1395555 Display terminal controller INTERNATIONAL BUSINESS MACHINES CORP 9 Aug 1972 [20 Aug 1971] 37126/72 Heading G4C The memory in a display terminal controller comprises a plurality of buffer memories, including a regeneration memory 18 (Fig. 3), which can receive data from and supply data to a retain memory 20 and a print memory 19 which can be fed from the regeneration memory 18. The buffer memories may receive data from a CPU via a receive buffer 17 or from a keyboard 22 and feed a cathode-ray tube display 21 or a printer 23. The memory is preferably part of a core memory having sections assigned to each terminal unit which the controller serves. All the controller functions are controlled by a micro program recorded in a read only memory. Data from the keyboard is stored in the buffer 18 and displayed on the screen at a position determined by a cursor, the cursor being controlled by the micro program to advance one position each time a new character is entered. When a protected character indicating the beginning of a protected area is encountered the cursor is advanced until an end protection is detected. When requested by the CPU data in buffer 18 is fed to the CPU starting at the first stored character and omitting characters in protected positions. Operation of a key results in display data from the keyboard or CPU being additionally printed. A particular line displayed on the C.R.T. may be selected and stored by positioning the cursor on the required line and then operating a selection key to transfer the selected data from the buffer 18 to the retain buffer 20. When a display key is pressed stored data in buffer 20 is transferred back to the buffer 18 and displayed, data stored from the keyboard being erased by this operation but data entered from the CPU being held. Data from the receive buffer 17 may be fed to buffer 18, via buffer 18 to buffer 20 and to buffer 19.