tmp89fm42l TOSHIBA Semiconductor CORPORATION, tmp89fm42l Datasheet - Page 390

• Manufacturer Part Number: tmp89fm42l
• Description: 8 Bit Microcontroller Tlcs-870/c1 Series
• Manufacturer: TOSHIBA Semiconductor CORPORATION

22.12
Security
RA003
22.12
22.12.1
party: password and security program functions.
22.12.1.1
22.12.1.2
In serial PROM mode, two security functions are provided to prohibit illegal memory access attempts by a third
mode or when the on-chip debugging function (hereafter called OCD) is used. Specifically, a password can be
established by using data (part of user memory) in flash memory. If a password is established, a password au-
thentication process must be performed to execute the flash memory read command, flash memory write
command, and other operation commands. In the case of the OCD, the password authentication process is required
prior to the start of the OCD system.
related restrictions that work in both serial and parallel PROM modes, the security program must be set to an
appropriate setting.
Security
A password is one of the security functions, and can be used when the TMP89FM42L operates in serial PROM
In parallel PROM mode, there are no access-related restrictions using a password. To establish the access-
as a password. A password thus specified is authenticated by comparing a password string transmitted by the
external controller with the memory data string of MCU where the password is specified. The area where a
password can be specified is 0x8000 through 0xFEFF in flash memory.
password structure (example of a transmitted password).
Passwords
With the TMP89FM42L, any piece of data in flash memory (8 or more consecutive bytes) can be specified
A password consists of three components: PNSA, PCSA, and a password string. Figure 22-4 shows the
How a password can be specified
Password structure
・ PNSA (password count storage address)
・ PCSA (password comparison start address)
・ Password string
fied address is the number of bytes of a password string. If the memory data is less than 0x07 or
if an address is outside the specified address range, a password error occurs.
is the starting address to be used to compare with a password string. If an address is outside the
specified address range, a password error occurs.
password string are compared by a specified number "N" of bytes; a comparison starts at an address
specified by PCSA. If there is a mismatch as a result of this comparison or if data of 3 or more
consecutive bytes is specified, a password error occurs, and the TMP89FM42L goes into an idle
state. In this idle state, external devices cannot communicate with the TMP89FM42L. To resume
communication, the TMP89FM42L must be restarted in serial PROM mode by using the reset pin.
A 3-byte address is specified in the area 0x8000 through 0xFEFF. The memory data of a speci-
The memory data specified here is defined as N.
A 3-byte address is specified in the area 0x8000 through 0xFEFF-N. An address thus specified
Data of 8 bytes to 255 bytes (=N) must be specified as a password string. Memory data and a
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TMP89FM42L