TXZ Family
Flash Memory
2018-06-05
99 / 120
Rev. 2.0
6.6.6.4. Password Determination
(1) Password verification using RAM transfer command
This item explains about the password determination No.5 described in “6.6.8. Communication Rules of RAM
If password area data deviates from the range of address, a password address error occurs. Also, if the same three
bytes data or more are continued, or the case where data is not all “0xFF”, a password error occurs as shown in
Password check flowchart”. If a password address error or a password area error is determined, an
ACK response is “0x11” regardless of the result of the password verification.
Then, received data (password data) is verified. Unless all N-byte data match the password in the flash memory,
a password error occurs. If a password error occurs, an ACK response is a password error.
When the security function is enabled, password verification is performed.
Figure 6.17 Password check flowchart
6.6.6.5. CHECKSUM Calculation
The CHECKSUM is calculated by 8-bit addition (ignoring the overflow) to transmit data and taking the two’s
complement of the sum of lower 8 bits. Use this calculation when the controller transmits the CHECKSUM value.
Example calculation of CHECKSUM
To calculate the CHECKSUM for 2 bytes data (“0xE5” and “0xF6”), perform 8-bit addition without signed.
0xE5 + 0xF6 = 0x1DB
Take the two’s complement of the sum to the lower 8-bit, and that is a checksum value. So, “0x25” is sent to the
controller.
0 - 0xDB = 0x25
