S71GS256 datasheet(78/195 Pages) SPANSION

78 / 195 page

S29GLxxxN MirrorBitTM Flash Family

S29GLxxxN_MCP_A1 December 15, 2004

Advan ce

In form ati o n

Reads and writes from the main memory are not allowed.

PPB Lock Bit Set Command

The PPB Lock Bit Set command is used to set the PPB Lock Bit to the “freeze state”

if it is cleared either at reset or if the Password Unlock command was successfully

executed. There is no PPB Lock Bit Clear command. Once the PPB Lock Bit is set

to the “freeze state”, it cannot be cleared unless the device is taken through a

power-on clear (for Persistent Protection Mode) or the Password Unlock command

is executed (for Password Protection Mode). If the Password Protection Mode Lock

Bit is programmed, the PPB Lock Bit status is reflected as set to the “freeze state”,

even after a power-on reset cycle.

PPB Lock Bit Status Read Command

The programming state of the PPB Lock Bit can be verified by executing a PPB

Lock Bit Status Read command to the device.

The Global Volatile Sector Protection Freeze Command Set Exit command

must be issued after the execution of the commands listed previously to reset the

device to read mode.

Volatile Sector Protection Command Set

The Volatile Sector Protection Command Set permits the user to set the Dynamic

Protection Bit (DYB) to the “protected state”, clear the Dynamic Protection Bit

(DYB) to the “unprotected state”, and read the logic state of the Dynamic Protec-

tion Bit (DYB).

The Volatile Sector Protection Command Set Entry command sequence

must be issued prior to any of the commands listed following to enable proper

command execution.

Note that issuing the Volatile Sector Protection Command Set Entry com-

mand disables reads and writes from main memory.

DYB Set Command

DYB Clear Command

The DYB Set and DYB Clear commands are used to protect or unprotect a DYB for

a given sector. The high order address bits are issued at the same time as the

code 00h or 01h on DQ7-DQ0. All other DQ data bus pins are ignored during the

data write cycle. The DYB bits are modifiable at any time, regardless of the state

of the PPB bit or PPB Lock Bit. The DYB bits are cleared to the “unprotected state”

at power-up or hardware reset.

—DYB Status Read Command

The programming state of the DYB bit for a given sector can be verified by writing

a DYB Status Read command to the device. This requires an initial access delay.

The Volatile Sector Protection Command Set Exit command must be issued

after the execution of the commands listed previously to reset the device to read

mode.

Note that issuing the Volatile Sector Protection Command Set Exit com-

mand re-enables reads and writes to the main memory.

S71GS256 Datasheet(PDF) 78 Page - SPANSION

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