Motorola MVME2400 Series Installation And Use Manual page 19

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 word is 16 bits, numbered 0 through 15, with bit 0 being the least
significant.
A longword is 32 bits, numbered 0 through 31, with bit 0 being the
least significant.
The terms control bit, status bit, true, and false 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.
xix