Motorola MVME172 - Manual (Page 4)

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.
Recent Updates
This edition of the MVME172 VME Embedded Controller Programmer’s Reference Guide
incorporates the following changes:
❏ The ‘‘MVME172 Version Register‘‘ section has an improved description of the
function of bit V6.
❏ The ‘‘PROM Access Time Control Register’’ and ‘‘Flash Access Time Control
Register’’ have clarification relating to bus speeds and access times with the
MVME172’s MC68060 processor.
❏ In accordance with recent MCG practice, the ‘‘Related Documentation’’ section
has been moved from the front of the document to a separate appendix.