readme.txtを元にREADME追加

added document for PCB2.x

bootloader compare bug fixed

supported PCB 2.x

control signal is changed phi2 is low when idle.

address bus set 0x3fff after bus closing

append programming guard filled 0 or 0xff

flash programming retry flag support

signature, address and length checking are added before firmware uptate

ドキュメントやコメントを整理

bootloader の実装完了、version 情報を特定アドレスに固定

bootloader update

bootloader is supporting ...

VRAM /CS direction is fixed