Offset Registers; Port Numbers - Motorola MVME187 Installation Manual

Offset Registers

Eight pseudo-registers (Z0 through Z7) called offset registers are
used to simplify the debugging of relocatable and position-
independent modules. The listing files in these types of programs
usually start at an address (normally 0) that is not the one at which
they are loaded, so it is harder to correlate addresses in the listing
with addresses in the loaded program. The offset registers solve
this problem by taking into account this difference and forcing the
display of addresses in a relative address+offset format. Offset
registers have adjustable ranges and may even have overlapping
ranges. The range for each offset register is set by two addresses:
base and top. Specifying the base and top addresses for an offset
register sets its range. In the event that an address falls in two or
more offset registers' ranges, the one that yields the least offset is
chosen.
Note

Port Numbers

Some 187Bug commands give the user the option to choose the port
to be used to input or output. Valid port numbers which may be
used for these commands are:
1. MVME187 EIA-232-D Debug (Terminal Port 0 or 00) (PORT 1
2. MVME187 EIA-232-D (Terminal Port 1 or 01) (PORT 2 on the
Relative addresses are limited to 1MB (5 digits),
regardless of the range of the closest offset register.
on the MVME187 P2 connector). Sometimes known as the
Òconsole portÓ, it is used for interactive user input/output by
default.
MVME187 P2 connector). Sometimes known as the Òhost
portÓ, this is the default for downloading, uploading,
concurrent mode, and transparent modes.
Entering Debugger Command Lines
5
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