pnx1500 NXP Semiconductors, pnx1500 Datasheet - Page 378

• Manufacturer Part Number: pnx1500
• Description: Pnx15xx Series Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX15XX_SER_3
Product data sheet
3.2.1 Shadow Registers
After completing the pool resource allocation and assigning each functional unit a
spot in the QVCP aperture map, the layer-specific functions can be configured. If a
pool resource has been assigned to a layer, its programming registers will occupy a
spot in this layer’s aperture map. For a layer without pool resource usage, the
particular spot in the aperture map will stay empty making sure that there is
symmetry in the programming register location for all the layers. If writes are
performed to an unoccupied spot they will be discarded. Reads will return zero.
Once all layer specific functions are set up, the output interface needs to be
programmed in order to correctly interface with the display controller chip. After
performing all these tasks the screen timing generator may be enabled. Once
running, the layers needed for the specific display scenario can be enabled. This
concludes the QVCP setup. Once the QVCP is set up for a certain scenario and
images are displayed, a number of operations can be reconfigured on the fly. Among
those functions are layer size and position, alpha blending and mixing functions as
well as color key and various other features.
Whenever any picture setting needs to be changed, it is always a good idea to make
it a seamless transition i.e., no noticeable artifacts should be observed by the general
audience. For most use cases, the goal is to change settings in between fields/frames
or during non-active video lines (e.g., VBI).
The QVCP provides two mechanisms (programmable/selectable via a register bit) for
register shadowing, whereby certain registers are shadowed to prevent screen
artifacts during the reconfiguration operations.
One method allows all new setting changes to really take effect at any line location
assigned by user. By using a duplicated set of the acting registers — the shadow
registers as they are commonly called — any register changes will first get buffered,
will wait for the correct time (i.e., the programmed line is the current line being
processed), and then be passed to acting registers. The contents of the shadow
registers are transferred to the corresponding active registers at the line location
indicated by 0x10E1F0[11:0]. The user has R/W access only to the shadow registers,
but not the active registers.
Besides a trigger from the line location indicated by the register at 0x10E1F0[11:0],
the second method comprises shadowing on a positive edge of the layer-enable
signal (i.e., when a disabled layer is enabled). The “positive edge” of layer enable
implies “when the layer_enable register changes from 0->1”. However, this positive
edge triggers only the shadow registers within that specific layer, all other layers’
shadow registers are not affected.
In conclusion, a shadow register transfers its content to an active register at
the positive edge of layer-enable, or
–
Once the aperture assignment has been determined, a matching resource
assignment to the data path has to be performed. This assures that the data
flow through the QVCP is switched through the proper resources assigned to
a specific layer and a specific-layer aperture. For details and an example
about resource and aperture allocation see
Rev. 3 — 17 March 2006
Section 3.3 on page
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX15xx Series
Chapter 11: QVCP
11-30.
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