Propeller Manual

PHSA, PHSB – Spin Language Reference
PHSA, PHSB
Register: Counter A and Counter B Phase Registers.
((PUB ┆ PRI))
PHSA
((PUB ┆ PRI))
PHSB
Returns: Current value of Counter A or Counter B Phase Register, if used as a source
variable.
Explanation
PHSA and PHSB are two of six registers (CTRA, CTRB, FRQA, FRQB, PHSA, and PHSB) that affect the
behavior of a cog’s Counter Modules. Each cog has two identical counter modules (A and B)
that can perform many repetitive tasks. The
PHSA and PHSB registers contain values that can
be directly read or written by the cog, but may also be accumulating with the value of
FRQA
and
FRQB, respectively, on potentially every System Clock cycle. See CTRA on page 95 for
more information.
Using PHSA and PHSB
PHSA and PHSB can be read/written like other registers or pre-defined variables. For example:
PHSA := $1FFFFFFF
The above code sets PHSA to $1FFFFFFF. Depending on the CTRMODE field of the CTRA
register, this value may remain the same, or may automatically increment by the value in
FRQA
at a frequency determined by the System Clock and the primary and/or secondary I/O pins.
See
CTRA, CTRB on page 95 for more information.
Note that in Propeller Assembly, the
PHSA and PHSB registers cannot be used in a read-modify-
write operation in the destination field of an instruction. Instead, separate read, modify, and
write operations (instructions) must be performed.
Keep in mind that writing to PHSA or PHSB directly overrides both the current accumulated
value and any potential accumulation scheduled for the same moment the write is performed.
Page 180 · Propeller Manual v1.1