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Certain areas of memory may be referred to as reserved memory in this reference manual.
Reserved — when referring to memory locations — implies that an implementation of the i960
architecture may use this memory for some special purpose. For example, memory-mapped
peripherals might be located in reserved memory areas on future implementations.
1.3.2
Specifying Bit and Signal Values
The terms set and clear in this manual refer to bit values in register and data structures. When a bit
is set, its value is 1; when the bit is clear, its value is 0. Likewise, setting a bit means giving it a
value of 1 and clearing a bit means giving it a value of 0.
The terms assert and deassert refer to the logically active or inactive value of a signal or bit,
respectively. A signal is specified as an active 0 signal by an overbar. For example, the input is
active low and is asserted by driving the signal to a logic 0 value.
1.3.3
Representing Numbers
All numbers in this manual can be assumed to be base 10 unless designated otherwise. In text,
binary numbers are sometimes designated with a subscript 2 (for example, 001
obvious from the context that a number is a binary number, the "2" subscript may be omitted.
Hexadecimal numbers are designated in text with the suffix H (for example, FFFF FF5AH). In
pseudo-code action statements in the instruction reference section and occasionally in text,
hexadecimal numbers are represented by adding the C-language convention "0x" as a prefix. For
example "FF7AH" appears as "0xFF7A" in the pseudo-code.
1.3.4
Register Names
Memory-mapped registers and several of the global and local registers are referred to by their
generic register names, as well as descriptive names which describe their function. The global
register numbers are g0 through g15; local register numbers are r0 through r15. However, when
programming the registers in user-generated code, make sure to use the instruction operand. i960
microprocessor compilers recognize only the instruction operands listed in
this manual, the registers' descriptive names, numbers, operands and acronyms are used inter-
changeably, as dictated by context.
Groups of bits and single bits in registers and control words are called either bits, flags or fields.
These terms have a distinct meaning in this manual:
bit
Controls a processor function; programmed by the user.
flag
Indicates status. Generally set by the processor; certain flags are user programmable.
field
A grouping of bits (bit field) or flags (flag field).
INTRODUCTION
1
). When it is
2
Table
1-1. Throughout
1-9
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