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Chapter 1 Introduction
4.How to Use This Document
■ Meaning of Bit Attribute Symbols
R : Readable
W : Writable
RM : Reading operation during read/modify/write operation.
“/” (Slash) R/W: Readable and writable. (The read value is the value written.)
“,” (comma) R,W: Values are different between read and write. (The read value is different from
the value written.)
R0 : The read value is “0”.
R1 : The read value is “1”.
W0 : Always write “0”.
W1 : Always write “1”.
(RM0) : read/modify/write operation reads “0”.
(RM1) : read/modify/write operation reads “1”.
RX : The read value is indeterminate. (Reserved bit or undefined bit)
WX : Writing does not affect the operation. (Undefined bit)
• Example of how R/W is used
• R/W : Readable and writable. (The read value is the value written.)
• R,W : Readable and writable. (The read value and written value are different.)
• R,RM/W : Readable and writable. (The read value and written value are different. Read/modify/write
command reads the value written.) Example: port data register
• R(RM1),W : Readable and writable. (The read value and written value are different. Read/modify/write
command reads 1.) Example: interrupt request flag
• R/WX : Read-only (Read-only. Writing does not affect the operation.)
• R1,W : Write-only (Write-only. The read value is 1.)
• R0,W : Write-only (Write-only. The read value is 0.)
• RX,W : Write-only (Write-only. The read value is indeterminate.)
• R/W0 : Reserved bit (The written value is 0. The read value is the value written.)
• R0/W0 : Reserved bit (The written value is 0. The read value is 0.)
• R1,W0 : Reserved bit (The written value is 0. The read value is 1.)
• RX,W0 : Reserved bit (The written value is 0. The read value is indeterminate.)
• R/W1 : Reserved bit (The written value is 1. The read value is the value written.)
• R1/W1 : Reserved bit (The written value is 1. The read value is 1.)
• R0,W1 : Reserved bit (The written value is 1. The read value is 0.)
• RX,W1 : Reserved bit (The written value is 1. The read value is indeterminate.)
• RX/WX : Undefined bit (The read value is indeterminate. Writing does not affect the operation.)
• R0/WX : Undefined bit (The read value is 0. Writing does not affect the operation.)