IPC@CHIP Documentation - SC12 @CHIP-RTOS V1.10

An out of range priority value (CX) will be limited to range 3..127 inside this function.
Note:
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Internally all tasks have a unique priority. When a task is createdor its priority is changed, that
task is given a lower internal task priority than any other task in the system with the same user
task priority.
RTOS Task Control Services
Interrupt 0xAD service 0x14: RTX_CREATE_SEM, Create a semaphore
Parameters
AH
BX:SI
CX
ES:DI
Create a resource or counting semaphore.
0x14 (= RTX_CREATE_SEM)
Pointer to 16 bit storage allocated by caller where this API will output a semaphoreID
Initial value:
Set to -1 for resource semaphore
Set in range [0 .. 32767] (inclusive) for counting semaphore
Pointer to 4 character unique name tag for the new semaphore, which need not be null terminated but
must contain four bytes.
Return Value
Comments
DX =0 success AX: 0, Location referenced by [BX:SI] contains the unique semaphoreID
DX!=0 failure AX: contains error code
A resource semaphore is created by setting CX = -1. A non-negative value in CX creates a counting
semaphore.
A resource semaphore is created in the free state, ready for use.
A counting semaphore is initially available the number of times specified in CX. The
RTX_SIGNAL_SEM API increments this count and semaphore access via RTX_GET_SEM or
RTX_WAIT_SEM decrements the count. A counting semaphore is not available when its count reaches
zero.
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