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High Byte
Low Byte
Register-Word Operation
Register
Memory
Operation
Memory
Un-
used
19 16 15
0
8 7
Unused
High Byte
Low Byte
Register-Byte Operation
High Byte
Low Byte
Byte-Register Operation
Register
Memory
Register
Memory
Operation
Memory
Operation
0
Register
Unused
Un-
used
0
19 16 15
0
19 16 15
0
8 7
8 7
Un-
used
CPU Registers
4.3.5 General-Purpose Registers (R4 to R15)
The 12 CPU registers (R4 to R15) contain 8-bit, 16-bit, or 20-bit values. Any byte-write to a CPU register
clears bits 19:8. Any word-write to a register clears bits 19:16. The only exception is the SXT instruction.
The SXT instruction extends the sign through the complete 20-bit register.
through
show the handling of byte, word, and address-word data. Note the reset
of the leading most significant bits (MSBs) if a register is the destination of a byte or word instruction.
shows byte handling (8-bit data, .B suffix). The handling is shown for a source register and a
destination memory byte and for a source memory byte and a destination register.
Figure 4-10. Register-Byte and Byte-Register Operation
and
show 16-bit word handling (.W suffix). The handling is shown for a source
register and a destination memory word and for a source memory word and a destination register.
Figure 4-11. Register-Word Operation
95
SLAU272C – May 2011 – Revised November 2013
CPUX
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