NXP Semiconductors QorIQ LS1012A Reference Manual

Table 23-10. Refresh rate example for REF_SEL = 0REFR[2:0] Number of refreshcommands every 64KHzAverage periodic refreshrate(tREFI)System Refresh period0x0 1 15.6 μs tRFC0x1 2 7.8 μs 2*tRFC0x3 4 3.9μs 4*tRFC0x7 8 1.95 μs 8*tRFCTable 23-11. Refresh rate example for REF_SEL = 2@ 400MHzREFR[2:0] Number of refreshcommands everyrefresh cycleREF_CNT Average periodicrefresh rate(tREFI)System Refreshperiod0x0 1 0x618 3.9 μs tRFC0x1 2 0xC30 3.9 μs 2*tRFC0x2 3 0x1248 3.9μs 3*tRFC0x3 4 0x1860 3.9 μs 4*tRFCOther refresh configurations are also allowed; the configuration values in the tables aboveare only examples for obtaining the desired average periodic refresh rate.If the required average periodic refresh rate (tREFI) is kept, all of the rows will berefreshed in every refresh window. Because the memory device issues additional refreshcommands for every refresh it receives, the tREFI remains the same across the device,regardless of its number of rows. This is particularly relevant in the tRFC parameter,which becomes bigger as the density increases.23.9.1.10.3 DiagramBits 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15R REF_CNTWReset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Bits 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31RREF_SELREFR0START_REFWReset 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0MMDC Memory Map/Register DefinitionQorIQ LS1012A Reference Manual, Rev. 1, 01/20181142 NXP Semiconductors