Motorola MC68VZ328 - Manual (Page 154)

9-4 MC68VZ328 User’s Manual
Reset
NOTE:
The MC68VZ328 does not provide autovector interrupts. At system
startup, the user interrupt vector must be programmed, thereby allowing
the processor to handle interrupts properly.
9.3 Reset
The reset exception corresponds to the highest exception level. A reset exception is processed for system
initialization and to recover from a catastrophic failure. Any processing that is in progress at the time of the
reset is aborted and cannot be recovered. Neither the program counter nor the status register is saved. The
processor is forced into the supervisor state. The interrupt priority mask is set at level 7. The address in the
first two words of the reset exception vector is fetched by the processor as the initial SSP (supervisor stack
pointer), and the address in the next two words of the reset exception vector is fetched as the initial
program counter.
At startup or reset, the default chip-select (CSA0) is asserted and all other chip-selects are negated. The
CSA0 signal should be used to decode an EPROM/ROM memory space. In this case, the first two long
words of the EPROM/ROM memory space should be programmed to contain the initial SSP and PC. The
initial SSP should point to a RAM space, and the initial PC should point to the startup code within the
EPROM/ROM space so that the processor can execute the startup code to bring up the system.
1A 26 104 068 SD Level 2 interrupt autovector
1B 27 108 06C SD Level 3 interrupt autovector
1C 28 112 070 SD Level 4 interrupt autovector
1D 29 116 074 SD Level 5 interrupt autovector
1E 30 120 078 SD Level 6 interrupt autovector
1F 31 124 07C SD Level 7 interrupt autovector
20–2F 32–47 128–188 080–0BC SD
TRAP instruction vectors
5
30–3F 48–63 192–255 0C0–0FF SD Unassigned, reserved 3
40–FF 64–255 256–1020 100–3FC SD User interrupt vectors
1.SP denotes supervisor program space and SD denotes supervisor data space.
2.Reset vector 0 requires four words, unlike the other vectors which only require two words, and it is located
in the supervisor program space.
3.Vector numbers 12–14, 16–23, and 48–63 are reserved for future enhancements by Motorola. No peripheral
devices should be assigned to these numbers.
4.The spurious interrupt vector is taken when there is a bus error indication during interrupt processing.
5.TRAP #n uses vector number 32 + n (decimal).
Table 9-1. Exception Vector Assignment (Continued)
Vector Number Address Number
Space 1 Assignment
Hex Decimal Decimal Hex