TMP92FD54AI datasheet(55/84 Pages) TOSHIBA

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92FD54AI-55

2006-01-27

TMP92FD54AI

(3) Basic operation

Essentially the flash memory on the TMP92FD54AI has the following two modes of

operation:

•

Mode in which data is read from memory (Read Mode)

•

Mode in which memory data is automatically erased/rewritten (Auto

Operation Mode)

Auto Operation Mode can be entered from Read Mode by the execution of a command

sequence. In Auto Operation Mode no data can be read from the flash memory.

1) Read

To read data, set the flash memory to Read Mode. The flash memory is

automatically placed in Read Mode immediately after power-on, after the CPU is

reset or when auto operation is terminated normally. If auto operation is

terminated abnormally, or if you want to return to Read Mode from another mode,

either use the Read/Reset command (software reset) or a hardware reset. These

are described below.

2) Writing commands

The method used for controlling flash memory commands complies with JEDEC

standards for standard E2PROMs. To write to the Command Register, execute a

command sequence on the flash memory. When the flash memory has latched the

input address and data into the Command Register, the program will executes the

instruction (see Tables 4.4.3 and 4.4.4).

Except for the fourth Read cycle of a Read/Reset and for the fourth Write cycle of

an Auto Program，only DQ0 to DQ7 are used to enter commands. Commands can

therefore be entered in byte units.

If you want to cancel command entry in the middle of a command sequence, enter

the Reset command. On accepting the Reset command, the flash memory resets

the Command Register and enters Read Mode. Likewise, if an erroneous command

sequence is entered, the flash memory resets the Command Register and enters

Read Mode.

3) Reset

•

Read/Reset command (software reset)

When auto operation terminates abnormally, the flash memory does not

automatically re-enter Read Mode. In this case use the Read/Reset command

to return the flash memory to Read Mode. Likewise, to cancel command entry

in the middle of a command sequence, use the Read/Reset command to clear

the contents of the Command Register.

•

Hardware reset

As shown in Figure 4.4.2, the flash memory has a reset input of its own. This

input is connected to the CPU’s Reset signal. Hence, if the CPU is reset

because the device’s RESET input pin is pulled Low (VIL) or because the

Watchdog timer has overflowed, the current flash memory operation, whether

a read operation (write or erase), will stop and the device will either remain in,

or re-enter, Read Mode.

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