Motorola MVME177 Installation And Use Manual page 103

The status codes stored in the MPCR are of two types:
The status codes that may be returned from the monitor are:
HEX 0 (HEX 00)
ASCII R (HEX 52)
ASCII E (HEX 45)
The status codes that may be set by the bus master are:
ASCII G (HEX 47)
ASCII B (HEX 42)
The Multiprocessor Address Register (MPAR), located in shared
RAM location of $804 offset from the base address the debugger
loads it at, contains the second of two longwords used to control
communication between processors. The MPAR contents specify
the address at which execution for the remote processor is to begin
if the MPCR contains a G or B. The MPAR is organized as follows:
At power-up, the debug monitor self-test routines initialize RAM,
including the memory locations used for multi-processor support
($800 through $807).
The MPCR contains $00 at power-up, indicating that initialization
is not yet complete. As the initialization proceeds, the execution
path comes to the ÒpromptÓ routine. Before sending the prompt,
this routine places an R in the MPCR to indicate that initialization
is complete. Then the prompt is sent.
If no terminal is connected to the port, the MPCR is still polled to
determine whether an external processor requires control to be
passed to the dual-port RAM. If a terminal does respond, the MPCR
is polled for the same purpose while the serial port is being polled
for user input.
Status returned (from the monitor)
Status set (by the bus master)
-- Wait. Initialization not yet complete.
-- Ready. The Þrmware monitor is watching for a change.
-- Code pointed to by the MPAR address is executing.
-- Use Go Direct (GD) logic specifying the MPAR address.
-- Install breakpoints using the Go (G) logic.
$804 * * *
Multiprocessor Support
* (MPAR)
B
B-23