Freescale Semiconductor MC68HC908MR32 - Manual (Page 37)

Monitor ROM
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 37
2.6 Monitor ROM
The 240 bytes at addresses $FE10–$FEFF are reserved ROM addresses that contain the instructions for
the monitor functions. See
18.3 Monitor ROM (MON) .
2.7 Random-Access Memory (RAM)
Addresses $0060–$035F are RAM locations. The location of the stack RAM is programmable. The 16-bit
stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Within page zero are 160 bytes of RAM. Because the location of the stack RAM is programmable, all page
zero RAM locations can be used for input/output (I/O) control and user data or code. When the stack
pointer is moved from its reset location at $00FF, direct addressing mode instructions can access
efficiently all page zero RAM locations. Page zero RAM, therefore, provides ideal locations for frequently
accessed global variables.
Before processing an interrupt, the central processor unit (CPU) uses five bytes of the stack to save the
contents of the CPU registers.
NOTE
For M68HC05 and M1468HC05 compatibility, the H register is not stacked.
$FFEE PWMMC vector (high)
$FFEF PWMMC vector (low)
$FFF0 FAULT 4 (high)
$FFF1 FAULT 4 (low)
$FFF2 FAULT 3 (high)
$FFF3 FAULT 3 (low)
$FFF4 FAULT 2 (high)
$FFF5 FAULT 2 (low)
$FFF6 FAULT 1 (high)
$FFF7 FAULT 1 (low)
$FFF8 PLL vector (high)
$FFF9 PLL vector (low)
$FFFA IRQ vector (high)
$FFFB IRQ vector (low)
$FFFC SWI vector (high)
$FFFD SWI vector (low)
High
$FFFE Reset vector (high)
$FFFF Reset vector (low)
Table 2-1. Vector Addresses (Continued)
Address Vector
Priority