DDSPUT, DDSINIT (III)        1/15/73        DDSPUT, DDSINIT (III)

NAME            ddsput -- put a character on display data set

SYNOPSIS        (file descriptor in r0)

                jsr     pc,ddsinit

                (character in r0)

                jsr     pc,ddsput

DESCRIPTION     These routines provide an interface to the Dis-

                play Data Set, a peculiar device which can be

                called by Picturephone sets and which will dis-

                play some of the ASCII character set and certain

                other graphics on the Picturephone screen.

                If the DC11 or other interface hardware is not

                already set up to talk to the Display Data Set,

                the ddsinit entry should be called with the ap-

                propriate file descriptor in r0.  On the only

                known DDS attached to UNIX, the associated spe-

                cial file is called "/dev/ttyc".  ddsinit also

                clears the display.

                Thereafter, characters may be displayed by call-

                ing ddsput.  To the extent possible, ddsput simu-

                lates an ordinary terminal.  Characters falling

                to the right of the 22X22 screen area are ig-

                nored; the 23rd line on the screen causes the

                screen to be erased and that line to be put at

                the top of the new display.  Certain ASCII char-

                acters are interpreted specially as follows:

                FF   clear screen, go to top left

                HT   expand to right number of spaces

                DC1  treat as reverse line feed (move N)

                DC2  move cursor 1 place right (move E)

                DC3  forward line feed (move S)

                DC4  backspace 1 position (move W)

                SO   enter graph mode

                SI   leave graph mode

                CR   put cursor at start of current line

                Graph mode allows display of the non-ASCII char-

                acters and will be described when hell freezes


                Lower-case ASCII alphabetics are mapped into up-

                per case.  Several ASCII non-alphabetic graphics

                are unavailable as well.  Also the lower right

                circle of the "%" character is missing.  Also one

                of the circuit cards in the DDS has a crack in it

                and sometimes it doesn't work.  All in all, it is

                best to avoid this device.

FILES           kept in /lib/liba.a

SEE ALSO        AT&T writeup on DDS


BUGS            yes