Motorola 700 Series, Installation And Use Manual

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Debugger General Information
3
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 every 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
MVME162LX dual-port RAM by issuing a remote
GO
command
using the VMEchip2 Global Control and Status Registers (GCSR).
The remote processor places the MVME162LX execution address in
general purpose registers 0 and 1 (GPCSR0 and GPCSR1). The
remote processor then sets bit 8 (SIG0) of the VMEchip2 LM/SIG
register. This causes the MVME162LX to install breakpoints and
begin 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
and Status Registers (LCSR) of the MVME162LX. The execution
address is formed by reading the GCSR general purpose registers
in the following manner:
GPCSR0 used as the upper 16 bits of the address
GPCSR1 used as the lower 16 bits of the address