SMJ34020A_06 Datasheet, PDF (11/97 Pages) Texas Instruments – GRAPHICS SYSTEM PROCESSOR

SMJ34020A
GRAPHICS SYSTEM PROCESSOR
SGUS011D − APRIL 1991 − REVISED SEPTEMBER 2004
transparency
Transparency is a mechanism that allows the surrounding pixels in an array to be specified as invisible. This
is useful for ensuring that only the object and not the rectangle surrounding it are written to the display. The
SMJ34020A provides four transparency modes:
D No transparency
D Transparency on result equal zero
D Transparency on source equal COLOR0
D Transparency on destination equal COLOR0
D Refer to the TMS34020 User’s Guide for more information.
I/O registers
The SMJ34020A contains an on-chip block of sixty-four 16-bit locations (mapped into the SMJ34020A’s
memory address space) that are used for I/O control registers. Eight of these are used by the host interface logic
and are not available to the user. Forty-seven I/O registers control parameters necessary to configure the
operation and report status of the following interfaces:
D Host interface
D Local memory
D Video timing
D Screen refresh
D External interrupts
D Internal interrupts
host interface registers
The host interface registers (HSTDATA, HSTADRL, HSTADRH, HSTCTLL, and HSTCTLH) are provided to
facilitate communications between the SMJ34020A and a host processor and maintain compatibility with the
SMJ34010. The registers are mapped into five of the I/O locations accessible to the SMJ34020A.
Two of these registers (HSTCTLL and HSTCTLH) are used to provide control by the host. This control consists
of the passing of interrupt requests, flushing the instruction cache, halting the SMJ34020A, transmitting a
non-maskable interrupt request to the SMJ34020A, enabling emulation interrupts, and setting host access
modes and configurations.
The other three registers are simple read/write registers to allow the SMJ34020A software to leave addresses
for the host at a known location and allow compatibility with some SMJ34010 software.
memory interface control registers
Some of the I/O registers are used to control various local memory interface functions, including:
D Frequency of DRAM refresh cycles
D Masking (read/write protection) of individual color planes
D DRAM row/column addressing configuration
D Accessing mode (big endian/little endian)
D Bus fault and retry recovery
video timing and screen refresh
Twenty-eight I/O registers are dedicated to video timing and screen refresh functions. The SMJ34020A can be
configured to drive composite sync or separate sync displays.
In composite sync mode, the SMJ34020A can be set to extract VSYNC and HSYNC from an external CSYNC
or it can be used to generate CSYNC from separate VSYNC and HSYNC inputs. Internally, the SMJ34020A
can be set to preset the horizontal and vertical counts on receipt of an external sync signal. This allows
compensation for any combination of internal and external delays that occur in the video synchronization
process.
The
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