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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 847
UG585 (v1.11) September 27, 2016
Appendix B: Register Details
Register DRAM_param_reg2 Details
Width 32 bits
Access Type rw
Reset Value 0x83015904
Description DRAM Parameters 2
Field Name Bits Type Reset Value Description
reg_ddrc_t_rcd 31:28 rw 0x8 tRCD - AL Minimum time from activate to read or
write command to same bank. Min value for this
is 1. AL = Additive Latency. DRAM Related.
reg_ddrc_rd2pre 27:23 rw 0x6 Minimum time from read to precharge of same
bank
DDR2: AL + BL/2 + max(tRTP, 2) - 2
DDR3: AL + max (tRTP, 4)
LPDDR2: BL/2 + tRTP - 1
AL: Additive Latency; BL: DRAM Burst Length;
tRTP: value from spec. DRAM related.
reg_ddrc_pad_pd 22:20 rw 0x0 If pads have a power-saving mode, this is the
greater of the time for the pads to enter power
down or the time for the pads to exit power down.
Used only in non-DFI designs.
Unit: clocks.
reg_ddrc_t_xp 19:15 rw 0x2 tXP: Minimum time after power down exit to any
operation. DRAM related.
reg_ddrc_wr2rd 14:10 rw 0x16 Minimum time from write command to read
command. Includes time for bus turnaround and
recovery times and all per-bank, per-rank, and
global constraints.
DDR2 and DDR3: WL + tWTR + BL/2
LPDDR2: WL + tWTR + BL/2 + 1
Unit: clocks.
Where, WL: Write latency. BL: burst length.
This must match the value programmed in the BL
bit of the mode register to the DRAM.
tWTR: internal WRITE to READ command delay.
This comes directly from the DRAM specs.