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(2) Read
When the upper byte is read from, the upper-byte value is transferred to the CPU and the lower-
byte value is transferred to TEMP. Next, when the lower byte is read from, the lower-byte value in
TEMP is transferred to the CPU.
These registers should always be accessed in 16-bit units at a time with a MOV instruction, and
the upper byte should always be accessed before the lower byte. Correct data will not be
transferred if only the upper byte or only the lower byte is accessed. Also note that a bit
manipulation instruction cannot be used to access these registers.
Example 1: Write to DACNT
MOV.W R0, @DACNT
; Write R0 contents to DACNT
Example 2: Read DADRA
MOV.W @DADRA, R0
; Copy contents of DADRA to R0
Table 9.3
Access Method for Reading/Writing 16-Bit Registers
Read
Write
Register Word
Byte
Word Byte
DADRA, DADRB
×
DACNT
×
×
[Legend]
Ο
: Indicates the allowed access. Word access includes continuous access to upper bytes
and lower bytes in that order.
×
: The result is not guaranteed in that access.
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