RTX51: PDATA AND DALLAS DS5002

Information in this article applies to:

• RTX51 Version 3.10

SYMPTOMS

I am using RTX51 with a Dallas DS5002. I have configured the device and my project so that SRAM is used for both CODE and XDATA memory. I am using P2 for the RPC.

When I run my program, it appears that RTX51 is writing to P2 and, therefore, making use of the RPC impossible. How do I tell RTX51 to use SRAM instead and not change P2?

CAUSE

RTX51 uses XDATA to store a Task Context Segment for each task. In order to speed up task switching and program execution, these segments are accessed as PDATA pages rather than XDATA. The result is that RTX51 changes the value on P2 to select the appropriate PDATA page.

RESOLUTION

When using RTX51 with the Dallas DS5002, it is necessary to place the Task Context Segments into XDATA memory, addressed via P0 and P2, rather than the SRAM. The result is that the RPC cannot be used since P2 is required for memory access.

MORE INFORMATION

• Refer to page 118 in the RTX51 User's Guide (04.98) for further information on the XDATA memory requirements of RTX51 and Task Context Segments.

Last Reviewed: Tuesday, July 19, 2005