Zilog Z16C30 - Manual (Page 193)

A-1
Z16C30 USC ®
U SER ' S M ANUAL Z ILOG
UM97USC0100
A.1 INTRODUCTION
U SER ’s M ANUAL
A
PPENDIX
A
A PPENDIX C HANGES
This is for the reader of previous USC documentation. It
summarizes the changes in the names of registers and
commands that were made in this document, with a few
words about why they were changed.
A.1.1 Transmit Status Blocks—>Transmit
Control Blocks
The names of registers and other USC features, in past
documentation, maintained the distinction between “sta-
tus” info as flowing from the USC to the host, and “control”
information as flowing from the host to the USC pretty
strictly — all except this one.
A.1.2 Interrupt Enable (for individual
sources) —> Interrupt Arm
There was no distinction between the enabling of a whole
interrupt type and the enabling of an individual source
within a type, and it seemed important to distinguish
between these, so we kept the former as “enabling” and
called the latter “arming” instead. Vague memories of early
minicomputer terminology say the same terms were used.
A.2 COMMANDS
A.2.1 Reload RCC / TCC —> Load RCC/TCC
It wasn’t clear why RCC and TCC were “reloaded” while
TC0 and TC1 were just “loaded”.
A.2.2 Select Straight/Swapped Memory
Data —> Select D15-8/D7-0 First
“Straight” means whichever way your microprocessor
wants it, while “swapped” is the way the other guys’ part
works.
A.2.3 Preset CRC —> Clear Tx/Rx CRC
Generator
More descriptive of the function: “preset” seemed to carry
the possibility that you might be able to load in any arbitrary
starting value.
A.3 BIT/FIELD NAMES
There weren’t really bit and field names in the old Technical
Manual — they were more like text titles. But for those bits
and fields that had fairly short titles, the names in this
manual may or may not be the same. One change of note
is that RCSR4 has been changed from “CV/EOF/EOM” to
“RxBound”, after it was noted that the bit has a fourth use:
in Nine-Bit mode it flags address bytes. (“CV/EOF/EOM/
Addr” seemed a little long) Another such change is that CCSR14 is now called RCCF
Avail rather than RCC Valid. (It’s perfectly valid for the RCC
FIFO to be empty, in which case there’s nothing available
to be read from it.) The bit and field names in this book are
similar to, but not identical with, those in the Electronic
Programmer’s Manual.
UM009402-0201