TVP4020
Programmers Reference Manual
Programming Model
7
0001.8000 ->
0001.FFFF
GP Registers
Yes
Table 3.2
Region 0 Address Map
3.1
P
ERMEDIA
as a Register file
The simplest way to view the interface to the P
ERMEDIA
Graphic
Processor is as a flat block of memory-mapped registers (i.e. a register
file). This register file appears as part of the address map for P
ERMEDIA
.
When a P
ERMEDIA
host software driver is initialized it can map the
register file into its address space. Each register has an associated
address tag, giving its offset from the base of the register file (since all
registers reside on a 64-bit boundary, the tag offset is measured in
multiples of 8 bytes). The most straightforward way to load a value into a
register is to write the data to its mapped address. In reality the chip
interface comprises a 256 entry deep FIFO, and each write to a register
causes the written value and the register’s address tag to be written as a
new entry in the FIFO.
Programming P
ERMEDIA
to draw a primitive consists of writing values to
the appropriate registers followed by a write to a command register. This
last write triggers the start of drawing.
P
ERMEDIA
has approximately 200 registers. All registers are 32 bits wide
and should be 32-bit addressed. Many registers are split into bit fields,
and it should be noted that bit 0 is the least significant bit.
In future chip revisions the register file may be extended and currently
unused bits in certain registers may be assigned new meanings.
Software developers should ensure that only defined registers are
written to and that undefined bits in registers are always written as
zeros. The only exception to this rule is that in certain registers it is
convenient to allow unmasked values to be written to registers which
hold numeric data. These fields are marked as "not used" in Appendix A
and elsewhere.
Register Types
P
ERMEDIA
has three main types of register:
•
Control Registers
•
Command Registers
•
Internal Registers
Control Registers are updated only by the host - the chip effectively uses
them as read-only registers. Examples of control registers are the
scissor clip min and max registers. Once initialized by the host, the chip
Содержание TVP4020 PERMEDIA 2
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