user manual

Memory Requirements
B-11
B
Memory Requirements
The program portion of 177Bug is approximately 512KB of code,
consisting of:
❏ Download
❏ Debugger
❏ Diagnostic packages
and is contained entirely in EPROM. The EPROM sockets on the
MVME177 are mapped starting at location $FF800000.
177Bug requires a minimum of 64KB of contiguous read/write
memory to operate.
The ENV command controls where this block of memory is located.
Regardless of where the onboard RAM is located, the first 64KB is
used for 177Bug stack and static variable space and the rest is
reserved as user space. Whenever the MVME177 is reset:
❏ Target PC is initialized to the address corresponding to the
beginning of the user space
❏ Target stack pointers are initialized to addresses within the
user space
❏ Target Interrupt Stack Pointer (ISP) set to the top of the user
space
At power-up or reset, all 8KB of memory at addresses $FFE0C000
through $FFE0DFFF is completely changed by the 177Bug initial
stack.