Preliminary
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Architecture
2.2
Architecture
2.2.1 DMM Functional Description
2.2.1.1
Priority Extension Generator (PEG)
The priority extension generator (PEG) is a dynamic software-programmable initiator-indexed table of
priorities. Its unique role is to generates priorities for each access forwarded by the DMM to the SDRAM
controller. For initiators that do not generate their own per-transaction priority, the priority value that is
programmed in the table, will be assigned to all SDRAM accesses generated by that initiator. These
priorities are not used by the DMM, for internal arbitrations.
The 16 priority entries are software-programmable with DMM_PEG_PRIO0 (for the first eight entries of the
ConnID table) and DMM_PEG_PRIO1 (for the last eight entries) registers and set on a 3-bit scale, ranging
from values 0-7, with Priority=0, being the highest priority.
When a request is passed to the SDRAM controller, the priority from the corresponding
DMM_PEG_PRIOx field for an initiator is passed to SDRAM. However, for HD_VPSS, the peripheral itself
generates a priority. The DMM_PEG_PRIOx field for HD_VPSS is bypassed and the priority indicated by
HD_VPSS access is sent to SDRAM controller.
2.2.1.2
ELLA
The Extra Low Latency Access (ELLA) of the DMM is a simple interface port for all accesses made by
Cortex™-A8. As the name suggests, this interface is simplified to reduce latency to the request from
Cortex™-A8. In this respect, the ELLA block:
•
Is limited to 1D bursts only
•
Is not capable of performing tiling conversions
•
Does not interact with the PAT block
The ELLA block main role is to split incoming requests at DMM atomic unit boundaries to ensure that
requests sent to the SDRAM controller fit in a single SDRAM page. More precisely, the ELLA block is
responsible for:
•
Allocating an internal response context to timely generate the appropriate responses
•
Splitting the incoming requests at DMM atomic section boundaries
•
Requesting internal buffer allocation in the appropriate ROBIN
•
In case of a write request, allocating and updating an internal write context to subsequently direct the
incoming write data into the relevant re-ordering buffer
NOTE:
In the Device, Cortex™-A8 accesses in the system address space of
8000 0000h-FFFF FFFFh, are only routed through ELLA port. Accesses made by
Cortex™-A8, in the all four tiled modes, including Paged mode, will be routed through the
TILER ports, thus not getting benefit of lower latency of the ELLA port.
ELLA sub-module is not software configurable.
2.2.1.3
LISA
The Local Interconnect and Synchronisation Agent (LISA) is a hardware interconnect module, aimed at
setting priorities, managing tags and memory mapping. LISA maps the system addresses on the incoming
DMM requests to the SDRAM addresses, as per the LISA sections programming.
LISA interconnect routes:
1. ELLA and TILER requests on the ROBIN initiator nodes.
2. ELLA and TILER write data on the ROBIN write buffers.
3. ROBIN read data to the relevant TILER initiators or to ELLA initiator.
The LISA block registers are DMM_LISA_MAP_i (i = 0 to 3) and DMM_LISA_LOCK.
335
SPRUGX9 – 15 April 2011
DMM/TILER
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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