1
Z85233
CPS DC-4058-03
C
USTOMER
P
ROCUREMENT
S
PECIFICATION
GENERAL DESCRIPTION
The Zilog Enhanced Mono Serial Communication Controller,
Z85233 EMSCC, is a software compatible CMOS member
of the SCC family introduced by Zilog in 1981. The EMSCC
is a full-duplex data communications controller capable of
supporting a wide range of popular protocols. The Z85233
EMSCC is a single channel version (Channel A) of Zilog's
Z85230 ESCC. Based on ZIlog's unique Superintegration
™
Technology, the EMSCC is compatible with designs using
Zilog's SCC and ESCC to receive and transmit data. It has
many improvements that significantly reduce CPU
overhead. The addition of a 4-byte transmit FIFO and an
8-byte receive FIFO significantly reduces the overhead
required to provide data to, and get data from, the transmitter
and receiver.
The EMSCC also has many features that improve packet
handling in SDLC mode. The EMSCC will automatically:
transmit a flag before the data, reset the Tx Underrun/EOM
latch, force the TxD pin high at the appropriate time when
using NRZI encoding, deassert the /RTS pin after the
closing flag, and better handle ABORTed frames when
using the 10x19 status FIFO. The combination of these
features along with the deeper data FIFOs significantly
simplifies SDLC driver software.
The CPU hardware interface has been simplified by reliev-
ing the databus setup time requirement and supporting
the software generation of the interrupt acknowledge
signal (/INTACK). These changes allow an interface with
less external logic to many microprocessor families while
maintaining compatibility with existing designs. I/O han-
dling of the EMSCC is improved over the SCC with faster
response of the /INT and /DTR//REQ pins.
The many enhancements added to the EMSCC permits a
system design that increases overall system performance
with better data handling and less interface logic.
Notes:
All Signals with a preceding front slash, "/", are active Low, e.g.:
B//W (WORD is active Low); /B/W (BYTE is active Low, only).
Power connections follow conventional descriptions below:
Connection Circuit Device
Power V
CC
V
DD
Ground GND V
SS
Z85233
EMSCC
™
ENHANCED MONO
SERIAL COMMUNICATION CONTROLLER
DC 4058-03 (11-4-94)
