U633H04SK45 데이터 시트보기 (PDF) - Zentrum Mikroelektronik Dresden AG

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U633H04SK45

PowerStore 512 x 8 nvSRAM

Zentrum Mikroelektronik Dresden AG 

Preliminary

U633H04

HSB NONVOLATILE STORE

The hardware controlled STORE Busy pin (HSB) is

connected to an open drain circuit acting as both input

and output to perform two different functions. When

driven LOW by the internal chip circuitry it indicates that

a STORE operation (initiated via any means) is in pro-

gress within the chip. When driven LOW by external cir-

cuitry for longer than tw(H)S, the chip will conditionally

initiate a STORE operation after tdis(H)S.

READ and WRITE operations that are in progress

when HSB is driven LOW (either by internal or external

circuitry) will be allowed to complete before the STORE

operation is performed, in the following manner.

After HSB goes LOW, the part will continue normal

SRAM operation for tdis(H)S. During tdis(H)S, a transition

on any address or control signal will terminate SRAM

operation and cause the STORE to commence.

Note that if an SRAM WRITE is attempted after HSB

has been forced LOW, the WRITE will not occur and

the STORE operation will begin immediately. HARD-

WARE-STORE-BUSY (HSB) is a high speed, low drive

capability bidirectional control line.

In order to allow a bank of U633H04s to perform syn-

chronized STORE functions, the HSB pin from a num-

ber of chips may be connected together. Each chip

contains a small internal current source to pull HSB

HIGH when it is not being driven LOW. To decrease the

sensitivity of this signal to noise generated on the PC

board, it has to be pulled to power supply via an exter-

nal resistor with a value such that the combined load of

the resistor and all parallel chip connections does not

exceed IHSBOL at VOL (see Figure 1 and 2).

If HSB is to be connected to external circuits other than

other U633H04s, an external pull-up resistor has to be

used.

During any STORE operation, regardless of how it was

initiated, the U633H04 will continue to drive the HSB

pin LOW, releasing it only when the STORE is com-

plete.

Upon completion of a STORE operation, the part will be

disabled until HSB actually goes HIGH.

HARDWARE PROTECTION

The U633H04 offers hardware protection against inad-

vertent STORE operation during low voltage condi-

tions. When VCAP < VSWITCH, all HSB initiated STORE

operations will be inhibited.

PREVENTING AUTOMATIC STORES

The PowerStore function can be disabled on the fly by

holding HSB HIGH with a driver capable of sourcing

15 mA at VOH of at least 2.2 V as it will have to over-

power the internal pull-down device that drives HSB

LOW at the onset of an PowerStore for 50 ns.

When the U633H04 is connected for PowerStore ope-

ration (see Figure 1) and VCCX crosses VSWITCH on the

way down, the U633H04 will attempt to pull HSB LOW;

if HSB does not actually get below VIL, the part will stop

trying to pull HSB LOW and abort the PowerStore

attempt.

DISABELING AUTOMATIC STORES

If the PowerStore function is not required, then VCAP

should be tied directly to the power supply and VCCX

should by tied to ground. In this mode, STORE opera-

tion may be triggered through the HSB pin. In either

event, VCAP (Pin 1) must always have a proper bypass

capacitor connected to it (Figure 2).

December 12, 1997

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