AM29BDD160G datasheet(26/79 Pages) AMD

26 / 79 page

Am29BDD160G

June 7, 2006

Initial Access Delay Configuration

The frequency configuration informs the device of the

number of clocks that must elapse after ADV# is

driven active before data will be available. This value

is determined by the input clock frequency.

SECTOR PROTECTION

The Am29BDD160 features several levels of sector

protection, which can disable both the program and

erase operations in certain sectors or sector groups

Sector and Sector Groups

The distinction between sectors and sector groups is

fundamental to sector protection. Sector are individual

sectors that can be individually sector protected/un-

protected. These are the outermost 4 kword boot sec-

tors, that is, SA0 to SA7 and SA38 to SA45. See

tables 11 and 12.

Sector groups are a collection of three or four adjacent

32 kword sectors. For example, sector group SG8 is

comprised of sector SA8 to SA10. When any sector in

a sector group is protected/unprotected, every sector

in that group is protection/unprotected. See Tables 11

and 12.

Persistent Sector Protection

A command sector protection method that replaces

the old 12 V controlled protection method.

Password Sector Protection

A highly sophisticated protection method that requires

a password before changes to certain sectors or sec-

tor groups are permitted

WP# Hardware Protection

A write protect pin that can prevent program or erase

to the two outermost 8 Kbytes sectors in the 75% bank

All parts default to operate in the Persistent Sector

Protection mode. The customer must then choose if

the Persistent or Password Protection method is most

desirable. There are two one-time programmable

non-volatile bits that define which sector protection

method will be used. If the customer decides to con-

tinue using the Persistent Sector Protection method,

they must set the Persistent Sector Protection

Mode Locking Bit. This will permanently set the part

to operate only using Persistent Sector Protection. If

the customer decides to use the password method,

they must set the Password Mode Locking Bit. This

will permanently set the part to operate only using

password sector protection.

It is important to remember that setting either the Per-

sistent Sector Protection Mode Locking Bit or the

Password Mode Locking Bit permanently selects

the protection mode. It is not possible to switch be-

tween the two methods once a locking bit has been

set. It is important that one mode is explicitly se-

lected when the device is first programmed, rather

than relying on the default mode alone. This is so

that it is not possible for a system program or virus to

later set the Password Mode Locking Bit, which would

cause an unexpected shift from the default Persistent

Sector Protection Mode into the Password Protection

Mode.

The WP# Hardware Protection feature is always avail-

able, independent of the software managed protection

method chosen.

Persistent Sector Protection

The Persistent Sector Protection method replaces the

old 12 V controlled protection method while at the

same time enhancing flexibility by providing three dif-

ferent sector protection states:

■ Persistently Locked—A sector is protected and

cannot be changed.

■ Dynamically Locked—The sector is protected and

can be changed by a simple command

■ Unlocked—The sector is unprotected and can be

changed by a simple command

Table 10.

Configuration Register After Device Reset

CR15

CR14

CR13

CR12

CR11

CR10

CR9

CR8

Reserve

IAD3

IAD2

IAD1

IAD0

DOC

1001110

CR7

CR6

CR5

CR4

CR3

CR2

CR1

CR0

Reserve

BL2

BL1

BL0

1100010

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