Motorola MVME166, Installation Manual

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Introduction
MVME166IG/D2 1-7
1
An asterisk (*) following the signal name for signals which are edge significant
denotes that the actions initiated by that signal occur on high to low transition.
In this manual, assertion and negation are used to specify forcing a signal to a
particular state. In particular, assertion and assert refer to a signal that is active
or true; negation and negate indicate a signal that is inactive or false. These
terms are used independently of the voltage level (high or low) that they
represent.
Data and address sizes are defined as follows:
❏
A byte is eight bits, numbered 0 through 7, with bit 0 being the least
significant.
❏
A two-byte is 16 bits, numbered 0 through 15, with bit 0 being the least
significant. For the MVME166 and other CISC modules, this is called a
word.
❏
A four-byte is 32 bits, numbered 0 through 31, with bit 0 being the least
significant. For the MVME166 and other CISC modules, this is called a
longword.
The terms control bit and status bit are used extensively in this document. The
term control bit is used to describe a bit in a register that can be set and cleared
under software control. The term true is used to indicate that a bit is in the
state that enables the function it controls. The term false is used to indicate that
the bit is in the state that disables the function it controls. In all tables, the
terms 0 and 1 are used to describe the actual value that should be written to
the bit, or the value that it yields when read. The term status bit is used to
describe a bit in a register that reflects a specific condition. The status bit can
be read by software to determine operational or exception conditions.