PIC24FJ128GC010 Datasheet, PDF (77/472 Pages) Microchip Technology – 16-Bit Flash Microcontrollers with 12-Bit Pipeline A/D, Sigma-Delta A/D, USB On-The-Go and XLP Technology

PIC24FJ128GC010 FAMILY
TABLE 4-41: EDS MEMORY ADDRESS WITH DIFFERENT PAGES AND ADDRESSES
DSRPAG
(Data Space Read
Register)
DSWPAG
(Data Space Write
Register)
Source/Destination
Address While
Indirect
Addressing
24-Bit EA
Pointing to EDS
Comment
x⁽¹⁾
x⁽¹⁾
0000h to 1FFFh
000000h to
Near Data Space⁽²⁾
001FFFh
2000h to 7FFFh
002000h to
007FFFh
001h
001h
008000h to
00FFFEh
002h
002h
010000h to
017FFEh
003h
•
•
•
•
•
1FFh
003h
•
•
•
•
•
1FFh
8000h to FFFFh
018000h to
0187FEh
•
•
•
•
FF8000h to
FFFFFEh
EPMP Memory Space
000h
000h
Invalid Address Address Error Trap⁽³⁾
Note 1:
2:
3:
If the source/destination address is below 8000h, the DSRPAG and DSWPAG registers are not considered.
This Data Space can also be accessed by Direct Addressing.
When the source/destination address is above 8000h and DSRPAG/DSWPAG are ‘0’, an address error
trap will occur.
4.2.6 SOFTWARE STACK
Apart from its use as a working register, the W15
register in PIC24F devices is also used as a Software
Stack Pointer (SSP). The pointer always points to the
first available free word and grows from lower to higher
addresses. It predecrements for stack pops and post-
increments for stack pushes, as shown in Figure 4-7.
Note that for a PC push during any CALL instruction,
the MSB of the PC is zero-extended before the push,
ensuring that the MSB is always clear.
Note:
A PC push during exception processing
will concatenate the SRL register to the
MSB of the PC prior to the push.
The Stack Pointer Limit Value register (SPLIM), associ-
ated with the Stack Pointer, sets an upper address
boundary for the stack. SPLIM is uninitialized at Reset.
As is the case for the Stack Pointer, SPLIM<0> is
forced to ‘0’ as all stack operations must be
word-aligned. Whenever an EA is generated using
W15 as a source or destination pointer, the resulting
address is compared with the value in SPLIM. If the
contents of the Stack Pointer (W15) and the SPLIM reg-
ister are equal, and a push operation is performed, a
stack error trap will not occur. The stack error trap will
occur on a subsequent push operation. Thus, for
example, if it is desirable to cause a stack error trap
when the stack grows beyond address, 2000h in RAM,
initialize the SPLIM with the value, 1FFEh.
Similarly, a Stack Pointer underflow (stack error) trap is
generated when the Stack Pointer address is found to
be less than 0800h. This prevents the stack from
interfering with the SFR space.
A write to the SPLIM register should not be immediately
followed by an indirect read operation using W15.
FIGURE 4-7:
0000h ₁₅
CALL STACK FRAME
0
PC<15:0>
000000000 PC<22:16>
<Free Word>
W15 (before CALL)
W15 (after CALL)
POP : [--W15]
PUSH : [W15++]
 2012-2013 Microchip Technology Inc.
DS30009312B-page 77