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A-1

Z16C30 USC

USER'S MANUAL

ZILOG

UM97USC0100

A.1 INTRODUCTION

SER

’s M

ANUAL

APPENDIX A

APPENDIX CHANGES

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

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