DP8418 datasheet(2/28 Pages) NSC

2 / 28 page

General Description (Continued)

In order to specify each device for ‘‘true’’ worst case operat-

ing conditions all timing parameters are guaranteed while

the chip is driving the capacitive load of 88 DRAMs includ-

ing trace capacitance The chip’s delay timing logic makes

use of a patented new delay line technique which keeps

AC skew to g3 ns over the full VCC range of g10% and

temperature range of b55 Cto a125 C The DP8417

DP8418 DP8419 and DP8419X guarantee a maximum

RASIN to CASOUT delay of 80 ns or 70 ns even while driv-

ing a 2 Mbyte memory array with error correction check bits

included Speed selected options of these devices are

shown in the switching characteristics section of this docu-

ment

With its four independent RAS outputs and nine multiplexed

address outputs the DP8419 can support up to four banks

of 16k 64k or 256k DRAMs Two bank select pins B1 and

B0 are decoded to activate one of the RAS signals during

an access leaving the three non-selected banks in the

standby mode (less than one tenth of the operating power)

with data outputs in TRI-STATE

The DP8419 has two mode-select pins allowing for two re-

fresh modes and two access modes Refresh and access

timing may be controlled either externally or automatically

The automatic modes require a minimum of input control

signals

A refresh counter is on-chip and is multiplexed with the row

and column inputs Its contents appear at the address out-

puts of the DP8419 during any refresh and are incremented

at the completion of the refresh RowColumn and bank

address latches are also on-chip However if the address

inputs to the DP8419 are valid throughout the duration of

the access these latches may be operated in the fall-

through mode

System Companion Components

Device

Function

DP84300

Programmable Refresh Timer for DP84xx DRAM Controller

DP84412

NS320081632 to DP8409A1718192829 Interface

DP84512

NS32332 to DP841718192829 Interface

DP84322

680000810 to DP8409A1718192829 Interface (up to 8 MHz)

DP84422

680000810 to DP8409A1718192829 Interface (up to 125 MHz)

DP84522

68020 to DP841718192829 Interface

DP84432

808688186188 to DP8409A1718192829 Interface

DP84532

80286 to DP8409A1718192829 Interface

DP8400-2

16-bit Expandable Error CheckerCorrector

DP8400-4

16-bit Expandable Error CheckerCorrector

DP8402A

32-bit Error Detector and Corrector (EDAC)

DP8418 Datasheet(PDF) 2 Page - National Semiconductor (TI)

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