DDR Bridge
Microsemi Proprietary UG0446 User Guide Revision 7.0
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DDR Bridge
The DDR bridge facilitates multiple AHB bus masters to access a single AXI slave and optimizes read
and write operations from multiple AHB masters to a single external DDR memory. The SmartFusion2
and IGLOO2 devices have three instances of the DDR bridge, one each for the MSS/HPMS, FDDR, and
MDDR subsystems, as shown in the following image. The DDR bridge implemented in the MSS/HPMS
(shown in red) provides an interface between AHB masters within the MSS/HPMS for accessing DDR
memory. The DDR bridge implemented in the MDDR subsystem (shown in green) provides an interface
between the user implemented AHB masters in the FPGA fabric for accessing DDR memory. Similarly,
the DDR bridge in the FDDR (shown in blue) subsystem facilitates fabric masters to access DDR
memory.
Figure 127 •
DDR Bridges in the SmartFusion2/IGLOO2 FPGA Device
The DDR bridge supports a single 64-bit AXI and up to four 32-bit AHB interfaces. For SmartFusion2 the
four MSS AHB masters are fixed, as shown in the following table. For Igloo2, the two HPMS AHB
MSS/HPMS
DDR Bridge
AHB Bus
Matrix
ARM
Cortex-M3
Processor
Cache
Controller
HPDMA
DDR
Bridge
DDR_FIC
MDDR Subsystem
MSS/HPMS
DDR
Memory
DDR
Memory
DDR
Bridge
DDR_FIC
FDDR Subsystem
Fabric
AHB
Master 0
AHB
Master 1
AHB
Master 1
AHB
Master 0
AXI
Transaction
Controller
AXI
Transaction
Controller
32-bit AHB
32-bit AHB
128-bit AHB
32-bit AHB
32-bit AHB
64-bit AXI
64-bit AXI
64-bit AXI
32-bit AHB
32-bit AHB
32-bit AHB
SmartFusion2/IGLOO2
M
S
S
S
S
M
M
M
M
M
M
M
M
M
M
S
S
S
S
S
S
S
D
D
R
I
O
D
D
R
I
O
Note:
Grey blocks and arrows indicate the steps happen only in MSS. Rest are same in SmartFusion2 and IGLOO2.