Peritek
5-6
Programming On-board Devices and Memories
5.2.2 Line Address Register (LAR)
The LAR selects a memory or device register group on the board and
permits a 1K Byte segment to be accessed through the DBR. Fully
configured, the board contains a number of programmable devices, each of
which has between 2 and 16 control registers. The board uses spare LAR
values (0 and 400) to permit access to all of these devices through the
DBR line buffer.
See Section 5.2.3 for A32 addressing information.
Note
The 34020 must be initialized prior to accessing memories or devices.
Table 5-3 LAR Bit Definitions
LAR
Memory Selected
0
34020 internal device registers. See Section 5.3 and 5.4 for
more information.
400
Device Buffer - Color map chip(s), DUARTs, PC Keyboard
controller, zoom register, cursors, and SCSI (
VCT/VCU
).
800
High Speed Data input port (HSP) - special order only
C00-CFF
Digital Lookup Table (
VCD-V
only)
2000-2FFF
Up to 2 MB of Flash EEPROM, using four 512 KB devices.
Video RAM
VCD-V and VCU-V
4000-5FFF
Primary (8-bit) graphics RAM - 1024 pixels for each LAR
value. 1K x 1K pixels is 1 MB or 1024 LARs. Memory is byte
addressable and writemask applies.
6000-7FFF
Overlay (4-bit) graphics RAM - 1024 pixels for each LAR
value. The data is valid in each byte, but only the 4 low bits
are used. Memory is byte addressable and writemask applies.
Содержание VCD-V
Страница 2: ...Peritek ...
Страница 3: ...Peritek ...
Страница 5: ...Peritek ...
Страница 6: ...Peritek ...
Страница 10: ...Peritek ...
Страница 41: ...Peritek 2 10 Installing Your Peritek Graphics Board Figure 2 2 Jumper Locations for the VCT V and VCU V ...
Страница 42: ...Peritek Installing Your Peritek Graphics Board 2 11 Figure 2 3 Jumper Locations for the VCD V ...
Страница 94: ...Peritek Theory of Operation 4 15 Figure 4 1 VCD V Block Diagram ...
Страница 95: ...Peritek 4 16 Theory of Operation Figure 4 2 VCU V Block Diagram ...
Страница 96: ...Peritek Theory of Operation 4 17 Figure 4 3 VCT V Block Diagram ...