
MFC2000 Multifunctional Peripheral Controller 2000
Hardware Description
24-22
Conexant
100723A
24.6 VIDEO/SCANNER INTERFACE
24.6.1 Function Description
The Video/Scan Interface connects the Video/Scan Controller to the SDRAM via DMA cycles. This interface has a
unidirectional data flow: Video/Scan Controller to SDRAM. It consists of two 64 halfword buffers that ping-pong,
address counters for Video/Scan Controller input, and CDRAM output and byte to halfword assembly.
The Video/Scan Controller transmits a single line when attached to the scanner input or a single frame when
attached to the video input. In either case, the Video/Scan Controller data flow is as follows:
1. The Video/Scan Controller initiates a transfer by a single high-going pulse on the start signal to VSI .
2. As each analog sample becomes available, it is placed on the VSC output bus and the data ready signal is
pulsed high to VSI. In the case of video capture, it is expected that the data ready signal will remain high for
long periods of time as video data is available at each rising edge of the data clock. In the case of scanner
capture, it is expected that the data ready signal will be inactive for several data clocks between successive
pixels.
3. As the Video/Scan Interface receives data from the Video/Scan Controller, it is assembled into halfwords and
then stored into one of the two ping-pong buffers. When the buffer is filled, data storing is switched to the
remaining buffer and a signal is passed to the opposite side of the interface indicating a buffer is available for
transfer.
4. The Video/Scan Controller terminates the transfer by a single high-going pulse on the stop signal.
5. On the Countach Bus Subsystem side of the Video/Scan Interface, the data flow is as follows:
6. A pulse is received from the Video/Scan Controller side of the Video/Scan Interface indicating a buffer is
available for transfer.
7. VSI asserts the DMA request signal to CBU. The sequencial DMA signal is also asserted if the buffer contains
more than one halfword of data.
8. Once the DMA acknowledge signal is detected, transfer begins, one data being transferred for each SDRAM
ready pulse.
24.6.2 Register Description
Address:
Video/Scanner
Interface Mode
(VSIMode)
$01FF8289
Address:
Video/Scanner
Interface Mode
(VSIMode)
$01FF8288
Bit 15
(Not Used)
Bit 14
(Not Used)
Bit 13
(Not Used)
Bit 12
(Not Used)
Bit 11
(Not Used)
Bit 10
(Not Used)
Bit 9
(Not Used)
Bit 8
(Not Used)
Default:
Rst. Value
xxh
Read Value
00h
Bit 7
(Not Used)
Bit 6
(Not Used)
Bit 5
(Not Used)
Bit 4
(Not Used)
Bit 3
(Not Used)
Bit 2
(Not Used)
Bit 1
Bit 0
Default:
Rst Value
xxxxxx00b
Read Value
00h
Video/Scanner
DMA Hog
Mode[1]
Video/Scanner
DMA Hog
Mode[0]
Bit 15-2
Bit 1-0
Not used
The Video/Scanner DMA Hog Mode field is used to throttle and/or
disable other DMA masters during video capture. It has the following
settings:
Hog Mode
Countach Subsystem Interface
Arm Bus Interface
0
Burst and single DMA allowed
Burst and single DMA allowed
1
No burst – single DMA only
No burst – single DMA only
2
No DMA allowed
No burst – single DMA only
3
No DMA allowed
No DMA allowed