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2007-10-15
TMP91FW60
14.6.6 Read Protect Set
The Read Protect Set command sequence applies read protection on the flash memory. When read protection
is applied, the flash memory cannot be read in Programmer mode and the RAM Transfer command cannot be
executed in Single Boot mode.
To cancel read protection, it is necessary to execute the Chip Erase command sequence. To check whether or
not read protection is applied, read xxx77EH in Product ID mode. It takes a maximum of 60 us to set read pro-
tection on the flash memory. Another command sequence cannot be executed until the read protection setting
has completed. This can be checked by reading the same address in the flash memory repeatedly until the same
data can be read consecutively. While a read protect operation is in progress, bit 6 of data is toggled each time
it is read.
14.6.7 Write Protect Set
The Write Protect Set command sequence applies write protection on the flash memory. When write protec-
tion is applied, the flash memory cannot be written to in Programmer mode and the RAM Transfer command
cannot be executed in Single Boot mode.
To cancel write protection, it is necessary to execute the Chip Erase command sequence. To check whether
or not write protection is applied, read xxx77EH in Product ID mode. It takes a maximum of 60 us to set write
protection. Another command sequence cannot be executed until the write protection setting has completed.
This can be checked by reading the same address in the flash memory repeatedly until the same data can be
read consecutively. While a write protect operation is in progress, bit 6 of data is toggled each time it is read.
14.6.8 Hardware Sequence Flags
The following hardware sequence flags are available to check the auto operation execution status of the flash
memory.
1. Data polling (D7)
When data is written to the flash memory, D7 outputs the complement of its programmed data until
the write operation has completed. After the write operation has completed, D7 outputs the proper
cell data. By reading D7, therefore, the operation status can be checked. While the Sector Erase or
Chip Erase command sequence is being executed, D7 outputs “0”. After the command sequence is
completed, D7 outputs “1” (cell data). Then, the data written to all the bits can be read after waiting
for 1 us.
When read/write protection is applied, the data polling function cannot be used. Instead, use the
toggle bit (D6) to check the operation status.
2. Toggle bit (D6)
When the Flash Memory Program, Sector Erase, Chip Erase, Write Protect Set, or Read Protect Set
command sequence is executed, bit 6 (D6) of the data read by read operations outputs “0” and “1”
alternately each time it is read until the processing of the executed command sequence has com-
pleted. The toggle bit (D6) thus provides a software means of checking whether or not the processing
of each command sequence has completed. Normally, the same address in the flash memory is read
repeatedly until the same data is read successively. The initial read of the toggle bit always returns
“1”.
Note:The flash memory incorporated in the TMP91FW60 does not have an exceed-time-limit bit (D5). It is therefore
necessary to set the data polling time limit and toggle bit polling time limit so that polling can be stopped if the
time limit is exceeded.