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layoutRead Device Status

The device contains a Status Register which may be read to find out whether program or erase operation is completed, and whetherthe program or erase operation is completed successfully. After writing 70h command to the command register, a read cycle outputsthe content of the Status Register to the I/O pins on the falling edge of CE or RE, whichever occurs last. This two line control allowsthe system to poll the progress of each device in multiple memory connections even when R/B pins are common-wired. RE or CEdoes not need to be toggled for updated status. Refer to table 3 for specific Status Register definitions. The command registerremains in Status Read mode until further commands are issued to it. Therefore, if the status register is read during a random readcycle, the read command(00h) should be given before starting read cycles.

Read ID

The device contains a product identification mode, initiated by writing 90h to the command register, followed by an address input of00h. Four read cycles sequentially output the manufacturer code(ECh), and the device code and 3rd cycle ID, 4th cycle ID respec-tively. The command register remains in Read ID mode until further commands are issued to it. Figure 13 shows the operationsequence

RESET

The device offers a reset feature, executed by writing FFh to the command register. When the device is in Busy state during randomread, program or erase mode, the reset operation will abort these operations. The contents of memory cells being altered are nolonger valid, as the data will be partially programmed or erased. The command register is cleared to wait for the next command, andthe Status Register is cleared to value C0h when WP is high. Refer to Table 4 for device status after reset operation. If the device isalready in reset state a new reset command will be accepted by the command register. The R/B pin changes to low for tRST after theReset command is written. Refer to Figure 14 below.

READY/BUSY

The device has a R/B output that provides a hardware method of indicating the completion of a page program, erase and randomread completion. The R/B pin is normally high but transitions to low after program or erase command is written to the command regis-ter or random read is started after address loading. It returns to high when the internal controller has finished the operation. The pin isan open-drain driver thereby allowing two or more R/B outputs to be Or-tied. Because pull-up resistor value is related to tr(R/B) andcurrent drain during busy(ibusy) , an appropriate value can be obtained with the following reference chart(Fig 15). Its value can bedetermined by the following guidance.


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