Possible to use a 256Mbit DDR DRAM IC on C5509A

Jimmy Fung

Is it possible to use a 256Mbit DDR DRAM IC on the C5509A? We only need need 64Mbit but due to availability, longevity and sourcing, we would like to use the newer 256Mbit devices. I have read the app notes and datasheets that all describe using 128Mbit devices. If there is any way a 256Mbit device can be used and only address 128Mbit or less that would be great.

In looking at the C5509A data sheet page 35 of 145, the maximum SDRAM size that is supported is 128Mbit. http://www.ti.com/lit/ds/symlink/tms320vc5509a.pdf

over 13 years ago

0 Steve Tsang over 13 years ago

TI__Mastermind 23785 points

C5509A only supports SDRAM, the timing diagrams on SPRU670A clearly show single data per clock cycle.

regards.

0 Jimmy Fung over 13 years ago in reply to Steve Tsang

Intellectual 575 points

sorry, I should have corrected the original question. Yes, it is SDRAM and not DDR. is there any way to support a 256Mb device? If it can be connected and just access only 128Mb, that is fine. Thanks.

0 Steve Tsang over 13 years ago in reply to Jimmy Fung

TI__Mastermind 23785 points

Bits 10-9 of SDRAM Control Register 1 (SDC1) define the type of SDRAM used. Only 64M and 128M are supported. Also, all 4 CE spaces are used in the 128M case. So, no 256M support. It looks ok to connect to a 256M chip. Please refer to figure 3-1 & 3-2 in SPRU670A. But I would expect a hang when addressing to higher than 128M space.

Regards.

0 Cong Van Nguyen over 13 years ago in reply to Steve Tsang

Intellectual 970 points

128Mb is the limit of a single C55x memory space. To achieve 256Mb, you need to use 2 separate mSDRAM chips and emulate chip select pins somehow (e.g. using GPIO).

Sorry, I've realized that refreshing control may not allow connecting multiple mSDRAM chips in parallel. The above method only works for "static" memories (SRAM, ROM, flash, etc).

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Possible to use a 256Mbit DDR DRAM IC on C5509A