TNETX3270

ThunderSWITCH24/3 ETHERNETSWITCH

WITH 24 10-MBIT/S PORTS AND 3 10-/100-MBIT/S PORTS

SPWS043B ± NOVEMBER 1997 ± REVISED APRIL 1999

SDRAM interface

The SDRAM interface observes two types of timing:

DMulticycle timings between commands

DSubcycle timings between signals and DCLK

Figure 16 illustrates the SDRAM interfaces signal timing in which each type of SDRAM command and its interrelated timings are shown. It is not intended to be representative of any particular receive or transmit buffer operation.

SDRAM command to command (see Figure 16)

SYMBOL

 

 

 

PARAMETER

 

 

 

MIN

MAX UNIT

tRSA

MRS to ACTV or REFR

 

 

 

 

 

 

24

ns

tRC

Row cycle time (ACTV to REFR to next ACTV or REFR)

 

 

 

120

ns

tRAS

Row active time (ACTV to DCAB)

 

 

 

 

 

72

ns

tRP

Row recharge time (DCAB to ACTV, REFR, or MRS)

 

 

 

36

ns

tRCD

Row to column delay (ACTV to READ or WRT)

 

 

 

36

ns

tAC3

Column access time [READ (CAS) latency] (READ to data sample)

 

 

36

ns

nCCD

Column address to column address (WRT to next READ or WRT, or READ to next READ)

24

ns

nCWL

Last data or write to new column address (WRT to next READ or WRT)

 

 

24

ns

tRWD

Read to write delay (READ to next WRT)

 

 

 

 

60

ns

tWR

Write recovery time (WRT to DCAB)

 

 

 

 

 

24

 

 

 

 

 

 

 

tRC

 

 

tRP

 

 

 

 

 

tRAS

 

 

 

 

 

 

 

 

tRWD

 

tWR

 

 

 

 

 

 

 

 

 

nCWL

 

 

 

 

 

tRSA

tRCD

tAC3

nCCD

 

tAC3

 

DCLK

 

 

 

 

 

 

 

 

 

 

 

 

MRS

ACTV

NOOP

NOOP

NOOP

WRT

 

DCAB

NOOP

 

NOOP

NOOP

NOOP

 

READ

NOOP

NOOP

READ

NOOP

REFR

DRAS

 

 

 

 

 

 

 

 

 

 

DCAS

 

 

 

 

 

 

 

 

 

 

DW

 

 

 

 

 

 

 

 

 

 

DD31±DD00

 

 

BUFFOP

 

 

READ1

WRITE

 

 

READ2

 

 

 

 

 

 

 

DA13±DA00

 

MODE

ROW

 

READ1

 

WRITE

READ2

XXXX

 

REGISTER

 

 

 

 

DA10=0

 

DA10=0

DA10=0

DA10=1

 

SETTINGS

 

 

 

 

 

 

 

 

 

 

Figure 16. SDRAM Command to Command

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Texas Instruments TNETX3270 specifications Sdram command to command see Figure