ACTF512K8 datasheet(8/21 Pages) AEROFLEX

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SCD1668 REV A 4/28/98

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If Data Polling or the Toggle Bit indicates the device has

been written with a valid erase command, D3 may be

used to determine if the sector erase timer window is still

open. If D3 is high ("1") the internally controlled erase

cycle has begun; attempts to write subsequent com-

mands to the device will be ignored until the erase oper-

ation is completed as indicated by Data Polling or Toggle

Bit. If D3 is low ("0"), the device will accept additional

sector erase commands. To ensure the command has

been accepted, the software should check the status of

D3 prior to and following each subsequent sector erase

command. If D3 were high on the second status check,

the command may not have been accepted. See Table 4

Sector Protection

Algorithims

SECTOR PROTECTION

The ACT-F512K8 features hardware sector protection

which will disable both program and erase operations to

an individual sector or any group of sectors. To activate

this mode, the programming equipment must force VID

on control pin OE and address pin A9. The sector

addresses should be set using higher address lines A18,

A17, and A16. The protection mechanism begins on the

falling edge of the WE pulse and is terminated with the

rising edge of the same.

To verify programming of the protection circuitry, the pro-

gramming equipment must force VID on address pin A9

with CE and OE at VIL and WE at VIH. Scanning the sec-

tor addresses (A16, A17, and A18) while (A6, A1, A0) =

(0, 1, 0,) will produce a logical "1" code at device output

D0 for a protected sector. Otherwise the device will read

00H for unprotected sector. In this mode, the lower order

addresses, except for 0, A1, and A6 are don't care.

It is also possible to verify if a sector is protected during

the sector protection operation. This is done by setting

A6 = CE = OE = VIL and WE = VIH (A9 remains high at

VID). Reading the device at address location XXX2H,

where the higher order addresses (A18, A17, and A16)

define a particular sector, will produce 01H at data out-

puts (D0 - D7) for a protected sector.

SECTOR UNPROTECT

The ACT-F512K8 also features a sector unprotect mode,

so that a protected sector may be unprotected to incor-

porate any changes in the code. All sectors should be

protected prior to unprotecting any sector.

To activate this mode, the programming equipment must

force Vid on control pins OE, CE, and address pin A9.

The address pins A6, A16, and A12 should be set to VIH.

The unprotection mechanism begins on the falling edge

of the WE pulse and is terminated with the rising edge of

the same.

It is also possible to determine if a sector is unprotected

in the system by writing the autoselect command and A6

is set at VIH. Performing a read operation at address

location XXX2H, where the higher order addresses (A18,

A17, and A16) define a particular sector address, will pro-

duce 00H at data outputs (D0-D7) for an unprotected

sector.

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