Enhanced PCI Bus Multimedia Controller
2.0 ARCHITECTURAL OVERVIEW
The ZR36057 architecture contains two main data paths, the
video path and the code path. The incoming video is processed
along the video path and transferred to the graphics display
memory using PCI DMA bursts.
In JPEG Decompression modes the code stream flows in the
opposite direction, from the system memory to the ZR36057
Code FIFO. The Codec Front End reads out the Code FIFO byte
by byte onto the Code Bus.
The ZR36057 Video Front End samples the video bus within a
programmable active field window, defined with repect to the
video synchronization signals. An optional vertical and horizon-
tal smooth scale down can be applied, in order to support
variable image sizes and variable PCI video data rate. The
scaled video stream can be converted to various RGB formats.
The converted pixels are packed and stored in a 256-byte Video
FIFO, organized as 64 32-bit doublewords. The stored video
pixels are read from the Video FIFO and transferred to the
graphics display memory according to a display masking map
controlled by and stored inside the ZR36057.
In MPEG Playback mode, the code stream is transferred to the
ZR36057 Code FIFO from the system memory. The code bytes
are read from the Code FIFO out to the Guest Bus.
The ZR36057 video and the code paths operate simultaneously
while the ZR36057 arbitrates the PCI bus requests for each
process.
Besides managing the Video and Code paths, the ZR36057
bridges the host CPU to peripheral devices (known as Guests).
Using a dedicated handshaking mechanism (the “PostOffice”
mechanism), host accesses to an internal ZR36057 register are
reflected to the Guest Bus in order to enable indirect host read
and write operations to the Guests.
The Code path is bidirectional. The data flow direction depends
on the mode of operation. The code stream (MPEG or JPEG) is
transferred between system memory and the internal Code
FIFO of the ZR36057 using PCI DMA bursts. The ZR36057
controls the transfer and addressing in both directions. The
Code FIFO size is 640 bytes, organized as 160 doublewords.
The ZR36057 contains a dedicated “Still Transfer” port which
enables data flow between the PCI interface and the Video Front
End. Using a specific handshake protocol, the host software
may transfer digitized video (RGB pixels) from the system
memory to the Video bus, and vice versa. This path enables very
fast transfer of still video images to be compressed or decom-
pressed by the JPEG codec.
In JPEG Compression modes the ZR36057 Codec Front End
fills the Code FIFO. From the Code FIFO the code is transferred
to the system memory, field by field.
Video DMA
Controller
VCLK, VCLKx2
VSYNC, HSYNC
FI
Video Front End
(VFE)
Video Input
Processor
RTBSY
Video FIFO
START, PXEN
Y[7:0]
UV[7:0]
B[7:0]
Application
Specific
GPIO[7:0]
Registers
SCL
SDA
2
I C Port
GCS[7:0]
GAD[2:0]
GRD, GWR
GRDY
Guest Bus
Master
Code DMA
Controller
GWS
GDAT[7:0]
Code FIFO
CEND
CCS
Codec Front End
(CFE)
CBUSY
CODE[7:0]
Interrupt
Manager
GIRQ[1:0]
Figure 2. ZR36057 Block Diagram
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