Chapter 10 Memory Subsystem.pdf

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NOTE: PASR Setting Before Entering Self-Refresh Mode:
Partial array self-refresh (PASR) allows memory accesses to all banks when the attached
memory is not in self-refresh. Software must ensure that after a self-refresh mode with PASR
field enabled on banks, only accesses to the refreshed parts of the memory are performed.
Failure to do so may result in fetching corrupted data.
10.2.5 SDRC Subsystem Basic Programming Model
This section contains programming guides on setting up the SMS and SDRC registers according to the
required application.
10.2.5.1 SMS Basic Programming Model
10.2.5.1.1 SMS Firewall Usage
Because region 0 always has level 0 priority, it can be masked by any protected region.
To configure a region:
1. Set the SMS.SMS_RG_ATTi register (where i is the region index from 0 to 7).
2. Set the SMS.SMS_RG_RDPERMi register.
3. Set the SMS.SMS_RG_WRPERMi register.
4. Set the SMS.SMS_RG_STARTj register (except for region 0. j is the region index from 1 to 7).
5. Set the SMS.SMS_RG_ENDj register (except for region 0. j is the region index from 1 to 7).
Region 0 is always active. There are no start and an end address for region 0. As soon as the
SMS.SMS_RG_STARTj[30:16] STARTADDRESS and SMS.SMS_RG_ENDj[30:16] ENDADDRESS
registers (where j = 1 to 7) are programmed, the firewall is activated. To prevent unexpected violations,
ensure that the protection regions do not overlap.
Region 1 ensures the proper dynamic programming of protection for regions 2 through 7. For example, the
protected region A is set and currently accessed, but it must be enlarged. To avoid deactivating region A
and exposing its content to unwanted leakage, region 1 can be used to mask this whole area during
reprogramming. When region A is correctly reprogrammed, region 1 can be deactivated.
When all the required regions are programmed, the locking mechanism allows freezing the configuration,
thus ensuring no further reprogramming.
10.2.5.1.2 VRFB Context Configuration
Using the RE requires several initialization programming steps. After an RE context is set up, an
application can use it transparently, as if addressing a frame buffer object with a standard raster-based
memory arrangement.
1. Define the page configuration. This operation usually depends only on the external memory device.
The same page settings are then applied to any newly created rotated frame buffer.
Consider an SDRAM device with 1024-byte pages. The page can be defined as a 16 * 64 array. The
page is not necessarily a square (32 * 32 is also a suitable value). It is recommended that the longest
side corresponds to the access direction requiring the maximum bandwidth.
In terms of register settings, in any context that uses that page size:
Page (page) width = 2 pw bytes (that is, pw = 6)
Page (page) height = 2 ph rows (that is, ph = 4)
2. The application must allocate the appropriate amount of memory in the SDRAM address space, as
required by the size of the frame buffer object.
Example: Create a 400 x 300 frame buffer, 16 bits per pixel
• Pixel size = 2 ps bytes (that is ps = 1)
• Number of pages per line: 400 * 2/64 = 12.5, rounded up to 13
• Number of pages per column: 300/16 = 18.75, rounded up to 19
In terms of register settings, the image size parameters correspond to the enlarged image, and are
2246 Memory Subsystem SPRUGN4L–May 2010–Revised June 2011
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