Zynq-7000 AP SoC and 7 Series FPGAs MIS v4.1
96
UG586 November 30, 2016
Chapter 1:
DDR3 and DDR2 SDRAM Memory Interface Solution
ui_clk_sync_rst
This is the reset from the UI which is in synchronous with
ui_clk
.
ui_clk
This is the output clock from the UI. It must be a half or quarter the frequency of the clock
going out to the external SDRAM, which depends on 2:1 or 4:1 mode selected in GUI.
init_calib_complete
The PHY asserts
init_calib_complete
when calibration is finished. The application has
no need to wait for
init_calib_complete
before sending commands to the Memory
Controller.
AXI4 Slave Interface Block
The AXI4 slave interface block maps AXI4 transactions to the UI interface to provide an
industry-standard bus protocol interface to the Memory Controller. The AXI4 slave interface
is optional in designs provided through the MIG tool. The RTL is consistent between both
tools. For details on the AXI4 signaling protocol, see the ARM AMBA
specifications
.
The overall design is composed of separate blocks to handle each AXI channel, which allows
for independent read and write transactions. Read and write commands to the UI rely on a
simple round-robin arbiter to handle simultaneous requests. The address read/address
write modules are responsible for chopping the AXI4 burst/wrap requests into smaller
memory size burst lengths of either four or eight, and also conveying the smaller burst
lengths to the read/write data modules so they can interact with the user interface.
If ECC is enabled, all write commands with any of the mask bits enabled are issued as
read-modify-write operation.
If ECC is enabled, all write commands with none of the mask bits enabled are issued as write
operation.