Info Catalog
as: MSP430-Chars
as: MSP430 Syntax
as: MSP430-Ext
9.28.2.3 Register Names
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General-purpose registers are represented by predefined symbols of the
form 'rN' (for global registers), where N represents a number between
'0' and '15'. The leading letters may be in either upper or lower case;
for example, 'r13' and 'R7' are both valid register names.
Register names 'PC', 'SP' and 'SR' cannot be used as register names
and will be treated as variables. Use 'r0', 'r1', and 'r2' instead.