Stack

Several options are available for stack configuration. The following EQUates define the size of the internal RAM used for stack area and the minimum free space on the stack. A macro allows you to specify code that is executed when there is there is not enough free stack on the CPU stack.

• RAMTOP specifies the top address for the on-chip stack. You should not change this unless you have IDATA variables located above the stack. The default setting is 0xFF.
• FREE_STACK specifies the minimum number of bytes available on the stack. When switching to a task, if RTX51 Tiny detects fewer than the value specified, the STACK_ERROR macro executes. A value of 0 disables stack checking. The default setting is 20 bytes.
• STACK_ERROR is a macro that specifies the instructions to execute in the event of a stack error (fewer than FREE_STACK bytes available). The default macro disables interrupts and enters an endless loop. For example:

  STACK_ERROR MACRO
  CLR EA ; disable interrupts
  SJMP $ ; endless loop if stack space is exhausted
  ENDM