Bulk Write/Erase - Video Enable Function - Control Data Corporation INFORMATION SYSTEMS TERMINAL II Hardware Maintenance Manual

TABLE 4-6. BULK WRITE/ERASE - VIDEO ENABLE FUNCTION
DATA BITS
OPERATION
2 1 0
0 0
X
Disable video
0
1
X
Enable video
1 0 0 Bulk erase and Disable video
1
0
1 Bulk write and Disable video
1 1 0 Bulk erase and Enable video
1 1 1
Bulk write and Enable video
X
=
o
or 1 irrelevant.
This function with Data Bits 1 and 2 equals 0 places the
terminal in nondisplay mode without affecting the display
memory contents. In this nondisplay mode, the video signal
to the monitor and to the composite video interface is
forced to the blanking state. The intended use of this
nondisplay mode is to allow blanking the display, if
desired, while the display memory space is being used as
extended program memory.
This function with Data Bit 2 equals 0 and Data Bit 1
equals 1 reenables the video to the monitor and to the com-
posite video interface (if previously disabled) without
affecting the display memory contents.
This function with Data Bit 2 equal to 1 initiates a hard-
ware write or erase of the complete refresh (display)
memory. The state of Data Bit 0 determines whether all ls
(Data Bit 0 equals 1) are written, giving a completely
illuminated display, or all Os (Data Bit 0 equals 0), pro-
ducing a totally blank (black) display. Either the bulk
write or bulk erase operation, when completed, also reen-
ables the video to the monitor and to the composite video
interface (if previously disabled). The full refresh
memory bulk write or erase takes about 14 milliseconds, and
writing data to the refresh memory should not be attempted
during this time as it may be destroyed. The Bulk Busy
status bit monitors this activity. Data Bits 2 through 7
are ignored during this output function as indicated in
table 4-6.
Read Upper
10
(Input 04) - This function is the same as
Read Lower
10;
but, transfers the remaining 8 bits.
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