Programming The Registers - Zenith Z-100 PC series Service Manual

Page ~.11
Circuit Description
The other 18 registers are selected by the pOinter information in the ad­
dress register, then the CPU directs the information at address 305 to
be loaded into the selected register. Transfers of address and parameter
information to and from the registers is via data lines DO through 07.
Programming the Registers
Table 3.2 defines individual registers in terms of values contained in them
and the results obtained with these values. All values are expressed in
hexadecimal.
Table 3.2. CRT Controller Register Functions
VALUES
REG. REG. REG. REG. 40
x
25 80
x
25 GRAPHICS
ADDR. NO. TYPE UNITS STAT. TEXT TEXT MODE
0 RO Horiz. Total
Char.
Write 38
71
38
1 R1 Horiz. Dispd. Char. Write 28 50 28
2 R2 Horiz. Sync. Char. Write 2D 5A 2D
Position
3 R3 Horiz. Sync. Char. Write OA OA
OA
4 R4 Vert. Total Row Write 1F 1F 7F
5 R5 Vert. Total Scan Write 06 06 06
Adjust Line
6 R6 Vert. Dispd. Row Write 19 19 64
7 R7 Vert. Sync. Row Write 1C 1C 70
Position
8 R8
Interlace Write 02 02 02
Mode
9 R9 Max. Scan Scan Write 07 07 01
Line Addr.
Line
A R10 Cursor Start Scan Write
06 06 06
Line
B
R11 Cursor End Scan Write 07
07
07
Line
C
R12
Start Addr. High Write 00 00 00
D
R13 Start Addr. Low Write 00 00
00
E R14
Cursor Addr. High Read/ XX
XX
XX
Write
F R15
Cursor Addr. Low Read/ XX XX
XX
Write
10 R16
Light Pen High
Read
XX
XX XX
11
R17
Light Pen Low
Read XX
XX
XX
xx
is a hexadecimal number from 00 to FF.