267
Stack growing direction
jsr sub1
4bytes
24bytes(PC+FLG+size of registers used
stack size used by sta_tsk)
36bytes(PC+FLG+size of registers used
stack size used by prcv _mbx )
sta_tsk
prcv_mbx
40by tes
When use register R2R0,R3 R1,A0(12bytes)

Figure 2.3:Example of Use Stack Size Calculation