T-Kernel Specification (1.B0.02)

5.5. IO PORT ACCESS SUPPORT FUNCTIONS 251
5.5 IO Port Access Support Functions
IO port access support functions are provided as library functions or C language macros. These can be
called from a task-independent portion or while dispatching and interrupts are disabled.
5.5.1 IO Port Access
In a system with separate IO space and memory space, an IO port access function accesses IO space.
In a system with memory-mapped IO only, an IO port access function accesses memory space. Using
these functions will improve software portability and readability even in a memory-mapped IO system.
—_w
—_h
—_b
Word (32-bit) units
Half-word (16-bit) units
Byte (8-bit) units
• void out_w( INT port, UW data )
• void out_h( INT port, UH data )
• void out_b( INT port, UB data )
port IO port address data Data to be written
Writes data to an IO port.
• UW in_w( INT port )
• UH in_h( INT port )
• UB in_b( INT port ) port IO port address return code Data to be read
Reads data from an IO port.
5.5.2 Microwait
• void WaitUsec( UINT usec )
• void WaitNsec( UINT nsec )
usec
nsec
Wait time (microseconds)
Wait time (nanoseconds)
Performs a microwait for the designated interval.
These waits occur in an ordinary busy loop, and as such are easily influenced by the runtime
environment, such as execution in RAM, execution in ROM, memory cache on or off, etc. These
wait times are therefore not very accurate.
These waits are not the same as an OS WAIT state. The system state remains as RUN state.
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T-Kernel 1.B0.02