HP 13255-91112 Display Controller Module Sep77 free download

File name 13255-91112_Display_Controller_Module_Sep77.pdf

HP 13255 DISPLAi CONTROLLER MODUL~ Manual Part No. 13255-91112 REv'ISED SEP-IO-77 DATA TERMINAL TECHNICAL INFORMATION HEWLETTi:j PACKARD Printed in U.S.A. 13255 13255-91112/02 Display Controller Module Rev SEP-10-77 1.0 INTRODUCTION. 1.1 GENERAL DESCkIPTIO~. The Display Controller ~odule is a high speed, special purpose 110 device. Its function is to provide drive signals to the CRT monitor, initiate data transfers from the terminal memorY, and convert ASCII characters into a video signal. The full screen capaoility Of the display is 24 rows of 80 characters each. The minimum system can display 64 characters with one display feature--inverse video fields. An additional 64-cha~acter ROM may be added to the baSic system for 128-character operation. The Display Memory Access PCA (OMA) is that portion of the Display Controller Module which reads characters from the memory, buffers them in BO-character shift registers, and sends them to the Display Timing and Display Control PCA's. The operation of the DMA is controlled by the Display Timing and Display Control PCA's which initiate the trans- fer of ~ows of characters. It should be noted that there are two possible Display Control PCAs. Unless otherwise noted, reference to the Display Control PCA will apply to both assemblies. 1.2 PACKAGING. The Display Controller Module consists Of three PCA's, the Display Control, Display Timing, and tne Display Memory Access PCA's. The DMA is adjacent to the Display Timing and Display Control PCA's and all three boards are connected together with tne Top Plane Connector Assem- bly. The connection to the CRT monitor is made with the Sweep Cable Assembly from the CRT monitor to the Display Timing peA. 1.3 CHARACTER FONT. The basic character cell is a 9-dot by 1S-scan line rectangle. ~ithin this cell is the 7 x 9 Character surrounded by one dot on either side for horizontal spacing, four scan lines below for lower case cnaracter descenaers, and one scan line above and oelow tor row-to-row spacinq. The appearance ot the characters is ennanced by means of a half-shift capability which generates smoother angles and curves by utilizing extra bits in the character ROMS. Eacn character scan line segment is stored in ROM as an 8-bit word. Seven of the bits (bITI-BIT7) corres- pond to the aot positions Dl-07 within the cnaracter cell. The eighth bit (BITO) controls whether the dots will occur durinq the normal 10t time