Motorola M5271EVB, Руководство пользователя

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1-8 M5271EVB User’s Manual
System Memory
changed by user software to map the external memory in different locations but the chip
select configuration such as wait states and transfer acknowledge for each memory type
should be maintained.
Chip Select usage:
External FLASH Memory CS0
External ASRAM Memory CS1
Table 1-2 shows the M5271EVB memory map.
1.2.5.1 Reset Vector Mapping
Asserting the reset input signal to the processor causes a reset exception. The reset
exception has the highest priority of any exception; it provides for system initialization and
recovery from catastrophic failure. Reset also aborts any processing in progress when the
reset input is recognized. Processing cannot be recovered.
The reset exception places the processor in the supervisor mode by setting the S-bit and
disables tracing by clearing the T bit in the SR. This exception also clears the M-bit and sets
the processor’s interrupt priority mask in the SR to the highest level (level 7). Next, the
VBR is initialized to zero (0x00000000). The control registers specifying the operation of
any memories (e.g., cache and/or RAM modules) connected directly to the processor are
disabled.
Once the processor is granted the bus, it then performs two longword read bus cycles. The
first longword at address 0 is loaded into the stack pointer and the second longword at
address 4 is loaded into the program counter. After the initial instruction is fetched from
memory, program execution begins at the address in the PC. If an access error or address
error occurs before the first instruction is executed, the processor enters the fault-on-fault
halted state.
The Memory that the MCF5271 accesses at address 0 is determined at reset by sampling
D[20:19].
Table 1-2. The M5271EVB Default Memory Map
Address Range Signal and Device
0x0000_0000 - 0x00FF_FFFF 16 Mbyte SDRAM
0x2000_0000 - 0x2000_FFFF 64 Kbytes Internal SRAM
0x3000_0000 - 0x300F_FFFF External ASRAM (not fitted)
0xFFE0_0000 - 0xFFFF_FFFF
or
0xFFC0_0000 - 0xFFFF_FFFF 2 Mbytes External Flash (U10)
or
4 Mbytes External Flash (U11)