USERSTACKDPP3 DIRECTIVE

Answer

Information in this article applies to:

C166 Version 4.06

QUESTION

What does the USERSTACKDPP3 directive do?

ANSWER

The USERSTACKDPP3 directive, abbreviated U3, changes the assumptions made by the C166 Compiler regarding accesses to the user stack area.

By default, the user stack is located in the NDATA memory area and is accessed with DPP2. To locate the user stack in the IDATA or SDATA memory classes (which is accessed using DPP3), you must use the USERSTACKDPP3 directive and you must make the following changes to the definition of the user stack and the initialization of the user stack pointer (R0) in the startup code:

The changes are highlighted and shown with 'SDATA'. 'IDATA' works the same way.

STARTUP.A66 or START167.A66

    ?C_USERSTACK   SECTION   DATA PUBLIC 'NDATA'
to:
    ?C_USERSTACK   SECTION   DATA PUBLIC 'SDATA'

    NDATA  DGROUP  ?C_USERSTACK
to:
    SDATA  DGROUP  ?C_USERSTACK

In addition, you must change the following line:

    MOV    R0,#DPP2:?C_USERSTKTOP
to:
    MOV    R0,#DPP3:?C_USERSTKTOP

START_V2.A66

    ?C_USERSTACK   SECTION DATA PUBLIC 'NDATA'
    :
    ?C_USERSTACK1  SECTION DATA PUBLIC 'NDATA'
    :
    ?C_USERSTACK2  SECTION DATA PUBLIC 'NDATA'
to:
    ?C_USERSTACK   SECTION DATA PUBLIC 'SDATA'
    :
    ?C_USERSTACK1  SECTION DATA PUBLIC 'SDATA'
    :
    ?C_USERSTACK2  SECTION DATA PUBLIC 'SDATA'

    NDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK1, ?C_USERSTACK2
    :
    NDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK1
    :
    NDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK2
    :
    NDATA  DGROUP  ?C_USERSTACK
to:
    SDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK1, ?C_USERSTACK2
    :
    SDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK1
    :
    SDATA  DGROUP  ?C_USERSTACK, ?C_USERSTACK2
    :
    SDATA  DGROUP  ?C_USERSTACK

In addition, you must change the following line:

    MOV    R0,#?C_USERSTKTOP1
    :
    MOV    R0,#?C_USERSTKTOP2
    :
    MOV    R0,#?C_USERSTKTOP
to:
    MOV    R0,#DPP3:?C_USERSTKTOP1
    :
    MOV    R0,#DPP3:?C_USERSTKTOP2
    :
    MOV    R0,#DPP3:?C_USERSTKTOP