PL460 datasheet(22/48 Pages) MICROCHIP

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PL460

Bootloader

Data Sheet

DS60001666D - 22

blow the desired fuses with the values in the corresponding Tamper register, the command (CMD =

0x000C) must be sent with any address and any data value.

The end of this writing process is indicated in the answer of the bootloader status command (CMD

= 0x0012). If the writing process is active, bit 0 of the answer is ‘1’. In other cases, all data of the

answer is ‘0’.

In the case of CONTROL_BOX, to activate the new values, it is also necessary to write the

CONTROL_FUSES values to the corresponding Tamper register (CMD = 0x0010).

7.4.4.

Read Process

The CMD = 0x0003 command reads a unique address.

The CMD = 0x0002 command reads several consecutive addresses. In this case the frame will be

composed of 32 bits for the address, 16 bits for the command and as many SCK pulses (always

multiple of 32) as needed to read data.

To read a fuse box, it must have been written previously in the corresponding Tamper register.

The content of Tamper registers KEY_ENC_BOX, KEY_TAG_BOX or CONTROL_BOX are written to the

buffer with the commands CMD = 0x000D, CMD = 0x000E and CMD = 0x0010, respectively. Once the

Tamper register is written, it can be read with the command CMD = 0x0011.

7.4.5.

Fuse Programming

To write control or key fuses, an external supply of 2.5V ±10% DC 50 mA supply must be connected

to the VZC pin. The voltage in VZC must be applied only after the PL460 is already powered

(Power On Considerations) and maintained during the entire fuse programming process. If fuses are

programmed in the system, the appropriate protection of VZC circuitry by means of a 10K resistor

must be implemented, as it is shown in the figure below.

Figure 7-2. Externally Fuse Programming Setup

The fuse programming commands are sent through SPI. In case of using an external fuses

programming controller, the host MCU SPI ports must be left in high-impedance mode to allow

the connection between the PL460 and the external fuses programming controller.

7.4.6.

Control Fuses

The control fuse box includes 128 OTP (One-time programming) fuse bits. Only some of them are

used to configure software security features, see table below. Reserved bits in the range 0 to 17

must not be modified. Bits from 18 to 128 are not used. The default status of all fuses is not set.

Fuse Bit

Name

Description

ENCRNOTPLAIN If it is set, secure mode is active

READ_AES_KEY If it is set, KEY_ENC and KEY_TAG cannot be read

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