Zilog Z16F2810 User Manual
Page 15
UM018809-0611
Manual Objectives
ZNEO
®
CPU Core
User Manual
xv
Example 1:
R1 is set to
F8H
.
Example 2:
32-bit hexadecimal value
1234_5678H
Bit Numbering
Bits are numbered in order of significance, from 0 to n–1 where 0 indicates the least sig-
nificant bit and n indicates the total number of bits.
For example, 8 bits of a memory byte are numbered from 0 to 7.
Registers, memory bytes, and binary values are illustrated with the highest-numbered bit
on the left and the lowest-numbered bit on the right.
For example, Bit 6 of the value
0100_0000B
is 1.
Brackets
In text, square brackets, [ ], indicate one or more bits of a register, memory location, or
bus. A colon between bit numbers indicates a range of bits. A comma between bit numbers
indicates individual bits as given below:
Example 1:
ADDR[31:0] refers to bit 31 through bit 0 of the ADDR bus or memory loca-
tion. ADDR[31] is the most significant bit (msb), and ADDR[0] is the least significant bit
(lsb). ADDR[31:24] is the most significant byte (MSB), and ADDR[7:0] is the least sig-
nificant byte (LSB).
Example 2:
If the value of R1[7:0] is 0100_0010B, the bits R1[6,2] are both 1.
Braces
The curly braces, { }, indicate a single register, memory address or bus created by concat-
enating combination of smaller registers, addresses, buses or individual bits.
For example, the 32-bit effective address {
FFFFH
, ADDR[15:0]} consists of a 16-bit
hexadecimal value (
FFFFH
) and a 16-bit direct address.
FFFFH
is the most significant
word (16 bits) and ADDR[16:0] is the least significant word of the resulting 32-bit
address.
Use of the Words Set, Reset and Clear
The word set indicates a 1 is stored in a register or memory bit or flag. The words reset or
clear indicates a 0 is stored in a register or memory bit or flag.
Use of the Terms LSB, MSB, lsb and msb
In this document, the terms LSB and MSB, when appearing in upper case, mean least sig-
nificant byte and most significant byte, respectively. The lowercase forms (lsb and msb)
mean least significant bit and most significant bit, respectively.