Motorola MVME187 manual Port Numbers, Offset Registers

Entering Debugger Command Lines

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 Relative addresses are limited to 1MB (5 digits), regardless of the range of the closest offset register.

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 on the MVME187 P2 connector). Sometimes known as the Òconsole portÓ, it is used for interactive user input/output by default.

2.MVME187 EIA-232-D (Terminal Port 1 or 01) (PORT 2 on the MVME187 P2 connector). Sometimes known as the Òhost portÓ, this is the default for downloading, uploading, concurrent mode, and transparent modes.

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