Zilog Z16C30 - Manual (Page 56)

4-7
Z16C30 USC ®
U SER ' S M ANUAL Z ILOG
UM97USC0100
4.4 DATA FORMATS AND ENCODING
The USC’s Transmitter and Receiver can handle data in
any of the eight formats shown in Figure 4-4. The
RxDecode
field in the Receive Mode Register (RMR15-13) controls
the format for the Receiver, and the
TxEncode field in the
Transmit Mode Register (TMR15-13) controls it for the
Transmitter. The channel interprets both fields as follows:
xMR15-13 Data Format
000 NRZ
001 NRZB
010 NRZI-Mark
011 NRZI-Space
100 Bi-phase-Mark
101 Bi-phase-Space
110 Bi-phase-Level
111 Differential Biphase-Level
Non-Return-to-Zero ( NRZ ) mode doesn’t involve any en-
coding: at the start of each bit cell the transmitter makes
TxD low for a 0 or high for a 1.
NRZB mode is similar except
that the transmitter and receiver invert the data: a low is a
1 and a high is a 0.
Figure 4-4. Data Formats/Encoding
NRZ
1 1 0 0 1 0 Data Bit:
NRZB
NRZI-Mark
NRZI-Space
Biphase-Mark
Biphase-Space
Biphase-Level
Differential
Biphase-Level
DPLL TxCLK (All Modes)
DPLL RxCLK (NRZ Modes)
DPLL RxCLK
(Biphase Modes)
Note: No assumption is made about the starting state of the serial data in this figure.
As a result, those encoding schemes that operate in terms of transitions rather than
levels are shown with dual traces corresponding to their two possible starting states.
UM009402-0201