About P4080RM

[393002032]

I have a P4080DS board ,we have two questions about DDR Memory Controller register:

1. about 11.4.9 DDR SDRAM control configuration 2
(DDRx_DDR_SDRAM_CFG_2 )

in this regiser bit24-25 is reserved ,but when I set bit 24 -25 as 00,it doesn't work;when

I set bit 24-25 as 01 ,it work well.can you tell me why?

2.about  11.4.10 DDR SDRAM mode configuration
(DDRx_DDR_SDRAM_MODE)  and 11.4.11 DDR SDRAM mode configuration 2
(DDRx_DDR_SDRAM_MODE_2)

these two registers are very important for different DDR rate,but I don't know how to config them in different DDR rate, the P4080RM didn't give us a detail explain ,Please give us more detail information about these two registers.Thank u very much!!

[Bulat]

1. Probably some other registers are set incorrectly. This mainly concerns DDRx_DDR_SDRAM_CFG and DDRx_DDR_SDRAM_MODE registers.

2. Those registers are used to set SDRAM's Mode registers MR0.. MR3. Take a look at a DDR3 data sheet for description of those registers. You can also look at AN4039 app note, it provides DDR_SDRAM_MODE and DDR_SDRAM_MODE_2 fields description.

Regards,

Bulat

[393002032]

we found the describtion of DDRx_DDR_SDRAM_CFG and DDRx_DDR_SDRAM_MODE registers,but we can't config these registers

many bits describe like this "

the value in this field should match the value of TIMING_CFG_X[X]"

we don't know how to match the value ,for example:

1.bits25-27,29 SDMODE[CASLAT]：

The value in this field must match the CAS latency programmed in TIMING_CFG_1. The
DRAM data sheet should be consulted to select the proper CAS latency value.

how to match the value？
2.bits 20-22 SDMODE[WR]：

Regardless of the value of DDR_SDRAM_CFG_2[OBC_CFG], the value of this bit
should be based on the tWR obtained from the DRAM data sheet. When
DDR_SDRAM_CFG_2[OBC_CFG] = 0, the value in this field should match the value of
TIMING_CFG_1[WRREC]. But when DDR_SDRAM_CFG_2[OBC_CFG] = 1, the value
in this field is two clock cycles value less than the value of TIMING_CFG_1[WRREC]

in this register there is only 3 bits but there are 4 bits in TIMING_CFG_1[WRREC], how to match these two values?

and so on,there are too much describtion like this,Please tell me how to match these registers detail,thanks

[Bulat]

1. CAS latency is defined by the SDRAM data rate. For example, for 1200MT/s CASLAT can be set to 8 clocks. This should be set in both, SDRAM's MR0, (DDR_SDRAM_MODE's bits 25-27, 29 = 1000) and TIMING_CFG_1 (bits 12-15 =1111).

2. We recommend to set DDR_SDRAM_CFG_2[OBC_CFG]=0, this simplifies your problem. This also requires following settings: DDR_SDRAM_CFG[8_BE]=1, DDR_SDRAM_MODE[30,31]=00.

Number of bits in the registers is not important, you need to read comments. For example, if SDRAM's MR0[WR]=001, then Write_Recovery=5clk. P4080's TIMING_CFG_1[WRREC]= 0101 also corresponds to 5clk Write Recovery time.

Regards,

Bulat