Motorola MVME177 manual Offset Registers

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Debugger General Information

An Ñ Address register n.

Xn Ñ Index register n (An or Dn).

dÑ Displacement (any valid expression).

bd Ñ Base displacement (any valid expression). od Ñ Outer displacement (any valid expression).

nÑ Register number (0 to 7). Rn Ñ Offset register n.

Note In commands with RANGE specified as ADDR DEL ADDR, and with size option W or L chosen, data at the second (ending) address is acted on only if the second address is a proper boundary for a word or longword, respectively

Offset Registers

Eight pseudo-registers (R0 through R7) 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

❏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.

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