6530 Programmer's Guide

Preface
6530 Programmer’s Guide v
Numbering
Convention
The bit-numbering convention used in this book differs from that
assigned to the Tandem NonStop Kernel systems. The Tandem system
numbering scheme is based on a 16-bit word (numbered 0-15) with bit 15
being the least significant bit (lsb). On the workstation or PC, the
numbering scheme is based on an 8-bit byte (numbered 7-0) with bit 0
being the least significant bit. In this manual, the 8-bit scheme refers to
data accessed in the workstation or PC.
Note In byte operations, the Tandem system allocates two bytes per
word rather than one byte per word. For example, the system
places the status bytes read from the workstation or PC into an
application buffer starting on a word boundary. This means that
the most significant byte from the workstation or PC is written
into bits 0-7 of the word addressed in the application buffer.
Tandem NonStop Kernel System:
Workstation or PC:
0123456789101112131415
Byte 0 Byte 1
lsb
76543210
Byte 1
lsb