
2nd frame
interrupt
Top field[n+1]
Frame[n+1]
Bottom field[n+1]
Bottom field
interrupt
4th frame
interrupt
Bottom field[n+1]
Bottom field
interrupt
3rd frame
interrupt
Top field[n+1]
Time
Capture frame[n+2]
1st frame interrupt
(output start)
Top field[n]
Frame[n]
Bottom field[n]
Bottom field
interrupt
CPU kicks the
VPIF module
2nd frame interrupt
(1st frame data is
already stored in
SDRAM)
Top field[n+1]
Frame[n+1]
Bottom field[n+1]
Bottom field
interrupt
4th frame interrupt
(3rd frame data is
already stored in
SDRAM)
Bottom field[n+1]
Bottom field
interrupt
3rd frame interrupt
(2nd frame data is
already stored in
SDRAM)
Top field[n+1]
Time
Capture frame[n+2]
1st frame interrupt
(storage start)
Top field[n]
Frame[n]
Bottom field[n]
Bottom field
interrupt
Frame[n-1]
CPU kicks the
VPIF module
Not captured
Architecture
1776
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Video Port Interface (VPIF)
First Interrupt from VPIF
NOTE:
The first vertical synchronization signal is defined as the transition from the L10 line to the
L11 line in the interlace mode or from the L4 line to the L5 line in the progressive mode.
For raw capture mode, the VPIF immediately starts to capture the data if you enable middle
of frame.
In channels 0 and 1, the VPIF starts to capture incoming picture data from the first vertical synchronization
signal after the CPU activates the VPIF with register configuration. The interrupt signal from the VPIF is
asserted when the vertical synchronization signal is received. So, no incoming data is written in memory
when the first interrupt is asserted from the VPIF (
Relationship Between the First Interrupt and Incoming
If the CPU uses this interrupt signal not only for the time interval between each video frame but also for
the timing to read the stored data from the defined area in memory. Note that the CPU has to ignore the
first interrupt signal from the VPIF.
Relationship Between the First Interrupt and Incoming Data
In channels 2 and 3, the VPIF starts to assert displaying picture data after the CPU activates the VPIF
with register configuration. The output displaying data is asserted from the VPIF just after the VPIF reads
the output data from memory (
Relationship Between the First Interrupt and Outgoing Data
).
So, any redundant data such as the frame[n - 1] area in
Relationship Between the First Interrupt and
is not necessary to be prepared. The relationship between the interrupt pulse activation
and the register configuration is the same as for capturing data.
Relationship Between the First Interrupt and Outgoing Data
If the
Relationship Between the First Interrupt and Outgoing Data
described relationship with the CPU
activates the VPIF and the incoming data and frame[n] start the L11 line for the interlace mode or the L5
line for the progressive mode, the VPIF starts the data store from frame[n+1] not frame[n]. The first frame
interrupt happens after frame[n] (at the 2nd frame interrupt in
Relationship Between the First Interrupt and
), because at the start of the incoming data, there is no first vertical synchronization signal.