Cursor Start Register - Zenith Data Systems Z-100 Series Installation Manual

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3.10
Genera.l Theory of Operation
• Cursor Start Register (R10)-This 7 bit, write-only register is used
to define the beginning position of the cursor within the character field
(scan line 0-15) and the blink rate of the cursor. The 5 low-order
bits define the beginning scan line of the cursor. The size of the cursor
is defined by both this data and R11. The high-order bits determine
the blink rate of the cursor as shown in Table 3.5. The default value
for this register is OSH (11 decimal).
Table 3.5. Cursor Start Register
BIT 6 BITS CURSOR DISPLAY MODE
0 0 Cursor on steady (used on this card)
0 1 No cursor is displayed
1 0 Cursor blinks at about a 4 Hz rate
1 1 Cursor blinks at about a 2 Hz rate
• Cursor End Register (R11)-This 5-bit, write-only register defines
the last scan line occupied by the cursor. If you want a cursor to
occupy the full character field, set the lower 5 bits of R10 to scan
line 0, and R11 register to scan line 14 (14th line). Similarly, if a single
line of the character space is to be used, both R10 and R11 would
be set to the same scan line number. The default value for this register
is OCH (12H).
• Start Address Registers (R12 and R13)-These read/write registers
contain the first address in RAM to be displayed (top-left corner of
the display). If the optional 8K x 8 RAM chips are installed, this regis-
ter can be used by the CPU to scroll the display. When the standard
RAM is used, the bottom of the display is not addressable if this value
is changed. R12 is the 6-bit, high-order address, and R13 is the 8-bit,
low-order address.
• Cursor Registers (R14 and R15)-These read/write registers deter-
mine location of the cursor. Register R14 contains the 6-bit, high-order
address, and R15 contains the 8-bit, low-order address.
• Light Pen Registers (R16 and R17)-These read-only registers lo-
cate the light pen strike. The 2-329 Card does not support this feature.