BM29F400B-90PC Ver la hoja de datos (PDF) - Unspecified

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BM29F400B-90PC

4MEGABIT (512K x 8/ 256K x 16) 5VOLT SECTOR ERASE CMOS FLASH MEMORY

Unspecified 

BRIGHT

Microelectronics

Inc.

Preliminary BM29F400T/BM29F400B

If the device is deselected during programming or erase, the device will draw active current until the

programming or erase operation is completed. In the standby mode the outputs are in a high

impedance state, independent of the OE input.

Output Disable Mode

With the OE input at a logic high level (VIH), output from the device is disabled. This will cause the

output pins to be in a high impedance state. It is shown in Table 1 that CE = VIL and WE = VIH for

Output Disable. This is to differentiate Output Disable mode from Write mode and to prevent

inadvertent writes during Output Disable.

Program and Erase Modes

Device programming and erase are accomplished via the command register. Contents of the register

serve as inputs to the internal state machine. Outputs of the state machine dictate the function of the

device.

The command register itself does not occupy any addressable memory locations. The register is a

latch used to store the commands along with the addresses and data information needed to execute

the command. The command register is written by bringing WE to VIL, while CE is at VIL and OE is

at VIH. Addresses are latched on the falling edge of WE or CE , whichever happens later, while data

is latched on the rising edge of WE or CE , whichever happens first. Standard microprocessor write

timings are used. Refer to AC Characteristics for Programming/Erase and their respective Timing

Waveforms for specific timing parameters.

Enable Sector Protect and Verify Sector Protect Modes

The BM29F400 has a hardware Sector Protect mode that disables both Programming and Erase

operation to the protected sector(s). There are total of 11 sectors in this device. The sector protect

feature is enabled using the programming equipment at the user's site. The device is shipped from

the BMI factory with all sectors unprotected.

To verify programming of the protection circuitry, the programming equipment must force VID on the

address pin A9 with CE and OE at VIL and WE at VIH. As shown in Table 2, scanning the sector

addresses while (A6, A1 and A0) = (0, 1, 0) will produce a 01H code at the device output pins for a

protected sector. In the Verify Sector Protect mode, the device will read 00H for an unprotected

sector. In this mode, the lower order addresses, except for A0, A1 and A6, are don't care. Address

locations with A1 = VIL are reserved for Electronic ID manufacturer and device codes. It is also

possible to determine if a sector is protected in-system by writing the Electronic ID command

(described in the Electronic ID command section below.)

Temporary Sector Unprotect Mode

The BM29F400 has a Temporary Sector Unprotect feature that allows the protect feature to be

temporarily suspended to change data in a protected sector in-system. The Temporary Sector

Unprotect mode is activated by setting the RESET pin to VID (11.5V - 12.5V).

In this mode, protected sectors can be programmed or erased by selecting the sector addresses.

Once VID is removed from the RESET pin, all previously protected sectors will be protected. Refer to

the Temporary Sector Unprotect algorithm and timing waveforms.

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