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Filename:
SAA7115_Datasheet.fm
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page 70
Last edited by H. Lambers
Philips Semiconductors
CS-PD Hamburg
CVIP2
Datasheet
SAA7115
Date:
10/23/01
Version:
0.67
8.5
Image port output interface (subaddresses 84H to 87H)
The output interface consists of a FIFO for video and for sliced text data, an arbitration circuit, which controls the mixed
transfer of video and sliced text data over the I-port and a decoding and multiplexing unit, which generates the 8 or 16-bit
wide output data stream and the accompanied reference and supporting information.
The clock for the output interface can be derived from an internal clock (decoder or X-port), from the second internal PLL
set (PLL2 and CGC2) or an externally provided clock which is appropriate for e.g. VGA and frame buffer. The clock can
be up to 33 MHz.
The scaler provides the following video related timing reference events (signals), which are available on pins as defined
by subaddresses 84H and 85H:
Output field ID
Start and end of vertical active video range
Start and end of active video line
Data qualifier or gated clock
Actually activated programming page (if CONLH is used)
Threshold controlled FIFO filling flags (empty, full, filled)
Sliced data marker.
The data stream at the scaler output is accompanied by a data valid flag (or data qualifier) or is transported using a gated
clock. The discontinuous output data after the scaling process can be output as they occur or the data may be packed
to continuous output lines by means of a trigger mechanism, which is controlled by a separate pulse generator
(see addresses F5H to FBH).
Clock cycles with invalid data on the I-port data bus (including the HPD pins in 16-bit output mode) are handled in two
differentways(controlledbyINS8086H[7]).Asbefore,invalidcyclesmaybemarkedwith00H,butadditionallyablanking
value insertion (80H and 10H) as required by ITU656 is now implemented.
The output interface also arbitrates the transfer between scaled video data and sliced text data over the I-port output.
The bits SLDOM (5DH) and VITX (86H) are used to control the arbitration.
As a further operation the serialization of the internal 32-bit Dwords to 8-bit or optional 16-bit output, as well as the
insertion of the extended ITU 656 codes (SAV/EAV for video data, ANC or SAV/EAV codes for sliced text data) are done
here.
For handshake with the VGA controller, or other memory or bus interface circuitry, programmable FIFO flags are
provided (see Section 8.5.2).