1999 Apr 02 11
Philips Semiconductors Product specification
Digital camera USB interface IC SAA8117HL
8.4 Transfer buffer
The transfer buffer module (see Fig.1) ensures a smooth
transfer of the data to the FIFO of the USB. Moreover the
transfer buffer can insert in band synchronization words in
the video data stream.
This function can be switched on and off with
SN_In band_Control in register CONTROL17_0.
The synchronization words can only be used with
non-compressed data streams and are formatted like
0x00 0xFF 0x<framecounter>7<linecounter>9.
The subscript denotes the number of bits and the frame
counter is circular incrementing.
The non-compressed data is formatted like:
4:2:0:<optional sync word><Y0><Y1><Y2><Y3>
<C0><C2><Y4><Y5><Y6><Y7><C4><C6>....,
4:2:2: <optional sync word><Y0><Y1><Y2><Y3>
<U0><V0><U2><V2><Y4>....,
where C denotes U-data in the even lines (0, 2, 4, etc.)
and V-data in the odd lines (1, 3, 5, etc.).
8.5 SNERT interface
In a USB camera the SAA8110G will operate on a clock
frequency which depends on the actual frame rate. For the
slowest frame rates, this frequency can be so low that the
SNERT communication is no longer functional over the
specified entire frequency range of the microcontroller.
The microcontroller must adapt its SNERT bus frequency
to a frequency appropriate for the current mode in which
the SAA8110G is operating.
The SAA8117HL itself is also partly controlled via SNERT.
The CIF formatter, compression engine and the PPG
function are controlled via SNERT. This SNERT interface
works independently from the frame rate and can always
be operated in the full frequency range.
8.6 Sensor pulse generator
The SAA8117HL incorporates a Pulse Pattern Generator
(PPG) function. The PPG can be used for PAL medium
resolution Sharp sensors (LZ2423) or compatible CCD
sensors. The SAA8117HL can also handle VGA type CCD
sensors, so a set of pulses is provided to simplify the use
of such sensors. Depending on the type of sensor, it will be
necessary to reformat these pulses externally according to
the sensor specification.
It should be noted that in case of medium resolution Sharp
or compatible sensors an external inverter driver is
required to convert the 3 V pulses into a voltage suitable
for the used CCD sensor. For the medium resolution Sharp
CCD sensor driver, the name of the pins to which the PPG
pulses must be connected are indicated between brackets
in the SAA8117HL pinning list (pins C3, B1 and B2 are not
used).
For both type of sensors the PPG generates 8 different
frame rates (see Table 6). The active video size is
512 × 288 for PAL and 640 × 480 for VGA. The total H × V
size is 685 × 292 for PAL and 823 × 486 for VGA.
It should be noted that additional HD pulses are added
during the vertical blanking interval to reach a total of
312 lines in PAL mode and 525 lines in VGA mode as
required by the SAA8110G.
The following registers are associated with the PPG:
• CONTROL17_0
• CONTROL17_2
• PPG_SHUTTERSPEED_0
• PPG_SHUTTERSPEED_1
• PPG_CLPOB_START_LSB
• PPG_CLPOB_STOP_LSB
• PPG_CLPDM_START_LSB
• PPG_CLPDM_STOP_LSB
• CLPMSB.
8.7 Pulse diagrams
For medium resolution CCD sensors (PAL):
• High-speed pulses, see Figs 4 and 5
• Horizontal pulses, see Fig.6
• Vertical pulses, see Figs 7 to 11.
For VGA-sensors:
• High-speed pulses, see Figs 12 to 14
• Horizontal pulses, see Fig.15
• Vertical pulses, see Figs 16 to 21.