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((PUB ┆ PRI))
DIRB [Pin(s)] (Reserved for future use)
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Returns: Current value of direction bits for I/O Pin(s) in Ports A or B, if used as a source variable.
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NOTE: DIRB is reserved for future use; the Propeller P8X32A does not include Port B I/O pins so only DIRA is discussed below.
DIRA is used to both set and get the current direction states of one or more I/O pins in Port A. A low (0) bit sets the corresponding I/O pin to an input direction. A high (1) bit sets the corresponding I/O pin to an output direction. All the DIRA register's bits default to zero (0) upon cog startup; all I/O pins are specified as inputs by that cog until the code instructs otherwise.
Each cog has access to all I/O pins at any given time. Essentially, all I/O pins are directly connected to each cog so that there is no hub-related mutually exclusive access involved. Each cog maintains its own DIRA register that gives it the ability to set any I/O pin's direction. Each cog's DIRA register is OR'd with that of the other cogs' DIRA registers and the resulting 32-bit value becomes the I/O directions of Port A pins P0 through P31. The result is that each I/O pin's direction state is the "wired-OR" of the entire cog collective. See I/O Pins on page for more information.
This configuration can easily be described in the following simple rules:
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The above code sets the entire DIRA register (all 32 bits at once) to a value that makes I/O pins 15, 13, 12, 7, 6, 5, 4, 1 and 0 to outputs and the rest to inputs.
Using the post-clear (~) and post-set (~~~) unary operators, the cog can set all I/O pins to inputs, or outputs, respectively; it's not usually desirable to set all I/O pins to outputs, however. For example:
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