SLUS724F September 2006 – January 2022
PRODUCTION DATA
In addition to the programmable 1024-bits of memory are 64 bits of status information contained in the EPROM STATUS memory. The STATUS memory is accessible with separate commands. The STATUS bits are EPROM and are read or programmed to indicate various conditions to the software interrogating the BQ2022A. The first byte of the STATUS memory contains the write protect page bits, that inhibit programming of the corresponding page in the 1024-bit main memory area if the appropriate write-protection bit is programmed. Once a bit has been programmed in the write protect page byte, the entire 32-byte page that corresponds to that bit can no longer be altered but may still be read. The write protect bits may be cleared by using the WRITE STATUS command.
The next four bytes of the EPROM STATUS memory contain the page address redirection bytes. Bits in the EPROM status bytes can indicate to the host what page is substituted for the page by the appropriate redirection byte. The hardware of the BQ2022A makes no decisions based on the contents of the page address redirection bytes. This feature allows the user's software to make a data patch to the EPROM by indicating that a particular page or pages should be replaced with those indicated in the page address redirection bytes. The ones complement of the new page address is written into the page address redirection byte that corresponds to the original (replaced) page. If a page address redirection byte has an FFh value, the data in the main memory that corresponds to that page are valid. If a page address redirection byte has some other hex value, the data in the page corresponding to that redirection byte are invalid, and the valid data can now be found at the ones complement of the page address indicated by the hexadecimal value stored in the associated page address redirection byte. A value of FDh in the redirection byte for page 1, for example, indicates that the updated data are now in page 2. The details for reading and programming the EPROM status memory portion of the BQ2022A are given in Section 7.5.4 section.
ADDRESS (HEX) | PAGE |
---|---|
00h | Write protection bits BIT0—write protect page 0 BIT1—write protect page 1 BIT2—write protect page 2 BIT3—write protect page 3 BIT4 to 7—bitmap of used pages |
01h | Redirection byte for page 0 |
02h | Redirection byte for page 1 |
03h | Redirection byte for page 2 |
04h | Redirection byte for page 3 |
05h | Reserved |
06h | Reserved |
07h | Factory programmed 00h |