48LM01 datasheet(25/40 Pages) MICROCHIP

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DS20006008C-page 25

48L512/48LM01

11.5

Polling Routine

When operating in the more common automatic store

and recall mode (AutoStore/AutoRecall), the master

can poll the RDY/BSY bit on power-up to see when the

SRAM is ready for new Read/Write commands. See

Figure 11-3 beginning with the “Send RDSR Instruction

to the Device”.

Polling can also be used if the user-initiated Software

Store and Software Recall commands are used. Polling

allows the application to query whether the EERAM

has completed the transfer operations between the

SRAM and EEPROM portions of the memory cell. This

polling routine can be initiated after every power-up to

confirm that AutoRecall has completed, or after the

user-executed Software Store and Software Recall

commands have started processing.

The polling routine is repeatedly sending a Read

STATUS Register (RDSR) command to determine if

the device has completed its self-timed internal store or

recall cycles (see Figure 11-3). If the RDY/BSY bit = 1

from RDSR, the write cycle is still in progress. If

RDY/BSY bit = 0 from RDSR, this indicates the

operation has ended. If the device is still in a busy state,

repeated RDSR commands can be executed until the

RDY/BSY bit = 0, signaling that the device is ready to

execute a new instruction.

With the 48L512/48LM01 device, it is also possible to

poll the busy flag by sending the RDSR command only

once, and repeatedly clocking out the data until the

busy bit is clear. Only the RDSR instruction is enabled

during the store and recall cycles.

FIGURE 11-3:

POLLING FLOW

YES

Send Store or Recall

Command

Deassert CS High to

Initiate Operation

Send RDSR

Instruction to the Device

Next Operation

RDY/BSY = 0?

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