R5F72115D160FPV datasheet(973/1228 Pages) RENESAS

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Section 21 Flash Memory

Rev. 2.00 May. 08, 2008 Page 949 of 1200

REJ09B0344-0200

21.8

Supplementary Information

21.8.1

Specifications of the Standard Serial Communications Interface in Boot Mode

The boot program activated in boot mode communicates with the host via the on-chip SCI of the

LSI. The specifications of the serial communications interface between the host and the boot

program are described below.

(1)

States of Boot Program

The boot program has three states.

1. Bit-rate matching state

In this state, the boot program adjusts the bit rate to match that of the host. When the chip

starts up in boot mode, the boot program is activated and enters the bit-rate matching state, in

which it receives commands from the host and adjusts the bit rate accordingly. After bit-rate

matching is complete, the boot program proceeds to the inquiry-and-selection state.

2. Inquiry-and-selection state

In this state, the boot program responds to inquiry commands from the host. The device, clock

mode, and bit rate are selected in this state. After making these selections, the boot program

enters the programming/erasure state in response to the transition-to-programming/erasure

state command. The boot program transfers the erasure program to RAM and executes erasure

of the user MAT and user boot MAT before it enters the programming/erasure state.

3. Programming/erasure state

In this state, programming/erasure are executed. The boot program transfers the program for

programming/erasure to RAM in line with the command received from the host and executes

programming/erasure. It also performs sum checking and blank checking as directed by the

respective commands.

Figure 21.19 shows the flow of processing by the boot program.

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