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WRITE MEMORY

bq2022

SLUS526F – OCTOBER 2002 – REVISED DECEMBER 2006

Read EPROM

Initialization and ROM

READ MEMORY Command

Address Low

Address High

Read and

Memory Until End

Read and

Command

F0h

Byte

Byte

Verify CRC

of EPROM

Verify CRC

Sequence

Memory

A0

A7 A8

A15

Figure 8. READ MEMORY/Field CRC

The WRITE MEMORY command is used to program the 1024-bit EPROM memory field. The 1024-bit memory

field is programmed in 8-byte segments. Data is first written into an 8-byte RAM buffer one byte at a time. The

contents of the RAM buffer is then ANDed with the contents of the EPROM memory field when the programming

command is issued.

Figure 9 illustrates the sequence of events for programming the EPROM memory field. After issuing a ROM

command, the host issues the WRITE MEMORY command, 0Fh, followed by the low byte and then the high

byte of the starting address. The bq2022 calculates and transmits an 8-bit CRC based on the WRITE command

and address.

If at any time during the WRITE MEMORY process, the CRC read by the host is incorrect, a reset pulse must be

issued, and the entire sequence must be repeated.

After the bq2022 transmits the CRC, the host then transmits 8 bytes of data to the bq2022. Another 8-bit CRC is

calculated and transmitted based on the 8 bytes of data. If this CRC agrees with the CRC calculated by the host,

the host transmits the program command 5Ah and then applies the programming voltage for at least 2500

µs or

the starting address.

The starting address can be any integer multiple of eight between 0000 and 007F (hex) such as 0000, 0008,

and 0010 (hex).

The WRITE DATA MEMORY command sequence can be terminated at any point by issuing a reset pulse

NOTE:

The bq2022 responds with the data from the selected EPROM address sent least

significant-bit first. This response should be checked to verify the programmed byte. If

the programmed byte is incorrect, then the host must reset the part and begin the

write sequence again.

For both of these cases, the decision to continue programming is made entirely by the host, because the

bq2022 is not able to determine if the 8-bit CRC calculated by the host agrees with the 8-bit CRC calculated by

the bq2022.

Prior to programming, bits in the 1024-bit EPROM data field appear as logical 1s.

8

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