MBM29F040C Ver la hoja de datos (PDF) - Spansion Inc.

Número de pieza

componentes Descripción

Fabricante

MBM29F040C

FLASH MEMORY CMOS 4M (512K × 8) BIT

Spansion Inc. 

MBM29F040C-55/-70/-90

Read/Reset Command

The read or reset operation is initiated by writing the Read/Reset command sequence into the command register.

Microprocessor read cycles retrieve array data from the memory. The device remains enabled for reads until the

command register contents are altered.

The device will automatically power-up in the read/reset state. In this case, a command sequence is not required

to read data. Standard microprocessor read cycles will retrieve array data. This default value ensures that no

spurious alteration of the memory content occurs during the power transition. Refer to the AC Read

Characteristics and Waveforms for the specific timing parameters.

Autoselect Command

Flash memories are intended for use in applications where the local CPU alters memory contents. As such,

manufacture and device codes must be accessible while the device resides in the target system. PROM

programmers typically access the signature codes by raising A9 to a high voltage (VID = 11.5 V to 12.5). However,

multiplexing high voltage onto the address lines is not generally desired system design practice.

The device contains an Autoselect command operation to supplement traditional PROM programming

methodology. The operation is initiated by writing the Autoselect command sequence into the command register.

Following the command write, a read cycle from address XX00H retrieves the manufacture code of 04H. A read

cycle from address XX01H returns the device code A4H. (see Table 3.) All manufacturer and device codes will

exhibit odd parity with the MSB (DQ7) defined as the parity bit.

Sector state (protection or unprotection) will be informed address XX02H.

Scanning the sector addresses (A16, A17, A18) while (A6, A1, A0) = (0, 1, 0) will produce a logical “1” at device

output DQ0 for a protected sector. The programming verification should be perform margin mode on the protected

sector. (See Table 2 and 3.)

To terminate the operation, it is necessary to write the Read/Reset command sequence into the register, and

also to write the Autoselect command during the operation, execute it after writing Read/Reset command

sequence.

Byte Programming

The device is programmed on a byte-by-byte basis. Programming is a four bus cycle operation. There are two

“unlock” write cycles. These are followed by the program setup command and data write cycles. Addresses are

latched on the falling edge of CE or WE, whichever happens later and the data is latched on the rising edge of

CE or WE, whichever happens first. The rising edge of CE or WE (whichever happens first) begins programming.

Upon executing the Embedded Program Algorithm command sequence, the system is not required to provide

further controls or timings. The device will automatically provide adequate internally generated program pulses

and verify the programmed cell margin.

The automatic programming operation is completed when the data on DQ7 is equivalent to data written to this

bit (See Write Operation Status section.) at which time the device returns to the read mode and addresses are

no longer latched. (See Table 6, Hardware Sequence Flags.) Therefore, the device requires that a valid address

to the device be supplied by the system at this particular instance of time. Hence, Data Polling must be performed

at the memory location which is being programmed.

Any commands written to the chip during this period will be ignored.

Programming is allowed in any sequence and across sector boundaries. Beware that a data “0” cannot be

programmed back to a “1”. Attempting to do so may either hang up the device (Exceed timing limits.), or result

in an apparent success according to the data polling algorithm but a read from reset/read mode will show that

the data is still “0”. Only erase operations can convert “0”s to “1”s.

Figure 13 illustrates the Embedded ProgramTM Algorithm using typical command strings and bus operations.

12

Share Link: