INFORMATION ADVANCE

TMS320TCI6618

Communications Infrastructure KeyStone SoC

SPRS688—February 2011

www.ti.com

 

7.11 DDR3 Memory Controller

The 64-bit DDR3 Memory Controller bus of the TMS320TCI6618 is used to interface to JEDEC standard-compliant DDR3 SDRAM devices. The DDR3 external bus interfaces only to DDR3 SDRAM devices; it does not share the bus with any other types of peripherals.

7.11.1 DDR3 Memory Controller Device-Specific Information

The TMS320TCI6618 includes one 64-bit wide 1.5-V DDR3 SDRAM EMIF interface. The DDR3 interface can operate at 800 mega transfers per second (MTS), 1033 MTS, and 1333 MTS.

Due to the complicated nature of the interface, a limited number of topologies will be supported to provide a 16-bit, 32-bit, or 64-bit interface.

The DDR3 electrical requirements are fully specified in the DDR Jedec Specification JESD79-3C. Standard DDR3 SDRAMs are available in 8- and 16-bit versions, allowing for the following bank topologies to be supported by the interface:

72-bit: Five 16-bit SDRAMs (including 8 bits of ECC)

72-bit: Nine 8-bit SDRAMs (including 8 bits of ECC)

36-bit: Three 16-bit SDRAMs (including 4 bits of ECC)

36-bit: Five 8-bit SDRAMs (including 4 bits of ECC)

64-bit: Four 16-bit SDRAMs

64-bit: Eight 8-bit SDRAMs

32-bit: Two 16-bit SDRAMs

32-bit: Four 8-bit SDRAMs

16-bit: One 16-bit SDRAM

16-bit: Two 8-bit SDRAM

The approach to specifying interface timing for the DDR3 memory bus is different than on other interfaces such as I2C or SPI. For these other interfaces, the device timing was specified in terms of data manual specifications and I/O buffer information specification (IBIS) models. For the DDR3 memory bus, the approach is to specify compatible DDR3 devices and provide the printed circuit board (PCB) solution and guidelines directly to the user.

A race condition may exist when certain masters write data to the DDR3 memory controller. For example, if master A passes a software message via a buffer in external memory and does not wait for indication that the write completes, when master B attempts to read the software message, then the master B read may bypass the master A write and, thus, master B may read stale data and, therefore, receive an incorrect message.

Some master peripherals (e.g., EDMA3 transfer controllers) will always wait for the write to complete before signaling an interrupt to the system, thus avoiding this race condition. For masters that do not have a hardware specification of write-read ordering, it may be necessary to specify data ordering via software.

If master A does not wait for indication that a write is complete, it must perform the following workaround:

1.Perform the required write.

2.Perform a dummy write to the DDR3 memory controller module ID and revision register.

3.Perform a dummy read to the DDR3 memory controller module ID and revision register.

4.Indicate to master B that the data is ready to be read after completion of the read in step 3. The completion of the read in step 3 ensures that the previous write was done.

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Copyright 2011 Texas Instruments Incorporated

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