Motorola MVME177, Installation And Use Manual

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Debugger General Information
B-24
B
An ASCII G placed in the MPCR by a remote processor indicates
that the Go Direct type of transfer is requested. An ASCII B in the
MPCR indicates that breakpoints are to be armed before control is
transferred (as with the
GO command).
In either sequence, an E is placed in the MPCR to indicate that
execution is underway just before control is passed to RAM. (Any
remote processor could examine the MPCR contents).
If the code being executed in dual-port RAM is to reenter the debug
monitor, a TRAP #15 call using function $0063 (SYSCALL
.RETURN) returns control to the monitor with a new display
prompt. Note that each time the debug monitor returns to the
prompt, an R is moved into the MPCR to indicate that control can
be transferred once again to a specified RAM location.
GCSR Method
A remote processor can initiate program execution in the local
MVME177 dual-port RAM by issuing a remote
GO command
using the VMEchip2 Global Control and Status Registers (GCSR).
The remote
GO command causes the following sequence:
❏
Remote processor places the MVME177 execution address in
general purpose registers 0 and 1 (GPCSR0 and GPCSR1)
❏
Remote processor sets bit 8 (SIG0) of the VMEchip2 LM/SIG
register
❏
MVME177 installs breakpoints and begins execution
The result is identical to the MPCR method (with status code B)
described in the previous section.
The GCSR registers are accessed in the VMEbus short I/O space.
Each general purpose register is two bytes wide, occurring at an
even address. The general purpose register number 0 is at an offset
of $8 (local bus) or $4 (VMEbus) from the start of the GCSR
registers. The local bus base address for the GCSR is $FFF40100. The
VMEbus base address for the GCSR depends on the group select
value and the board select value programmed in the Local Control