Rainbow-electronics ATmega128RFA1 Uživatelský manuál stáhnout pdf (Strana 488)

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8266A-MCU Wireless-12/09

ATmega128RFA1

Figure 31-19. State Machine Sequence for Changing/Reading the Data Word

Test-Logic-Reset

Run-Test/Idle

Shift-DR

Exit1-DR

Pause-DR

Exit2-DR

Update-DR

Select-IR Scan

Capture-IR

Shift-IR

Exit1-IR

Pause-IR

Exit2-IR

Update-IR

Select-DR Scan

Capture-DR

1 1 1

0 0

1 1

31.9.11 Flash Data Byte Register

The Flash Data Byte Register provides an efficient way to load the entire Flash page

buffer before executing Page Write, or to read out/verify the content of the Flash. A

state machine sets up the control signals to the Flash and senses the strobe signals

from the Flash, thus only the data words need to be shifted in/out.

The Flash Data Byte Register actually consists of the 8-bit scan chain and an 8-bit

temporary register. During page load, the Update-DR state copies the content of the

scan chain over to the temporary register and initiates a write sequence that within 11

TCK cycles loads the content of the temporary register into the Flash page buffer. The

AVR automatically alternates between writing the low and the high byte for each new

Update-DR state, starting with the low byte for the first Update-DR encountered after

entering the PROG_PAGELOAD command. The Program Counter is pre-incremented

before writing the low byte, except for the first written byte. This ensures that the first

data is written to the address set up by PROG_COMMANDS, and loading the last

location in the page buffer does not make the Program Counter increment into the next

page.

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