Exar Corporation 48720 Kato Road, Fremont CA, 94538 (510) 668-7000 FAX (510) 668-7017 www.exar.com
ST16C2552
2.97V TO 5.5V DUAL UART WITH 16-BYTE FIFO
SEPTEMBER 2010
REV. 4.2.2
GENERAL DESCRIPTION
The ST16C2552 (2552) is a dual universal
asynchronous receiver and transmitter (UART). The
ST16C2552 is an improved version of the PC16552
UART. The 2552 provides enhanced UART functions
with 16 byte FIFOs, a modem control interface, and
data rates up to 4 Mbps. Onboard status registers
provide
the
user
with
error
indications
and
operational status. System interrupts and modem
control features may be tailored by external software
to meet specific user requirements. Indepedendent
programmable baud rate generators are privded to
select transmit and receive clock rates from 50 Bps to
4 Mbps. The baud rate generator can be configured
for either crystal or external clock input. An internal
loop-back capability allows onboard diagnostics. The
2552 provides block mode data transfers (DMA)
through FIFO controls. DMA transfer monitoring is
provided through the signals TXRDY# and RXRDY#.
An Alternate Function Register provides the user with
the ability to initialize both UARTs concurrently. The
2552 is available in the 44-PLCC package.
APPLICATIONS
Portable Appliances
Telecommunication Network Routers
Ethernet Network Routers
Cellular Data Devices
Factory Automation and Process Controls
FEATURES
Added feature in devices with top marking "A2
YYWW" and newer:
■ 5 Volt Tolerant Inputs
Pin-to-pin and functionally compatible to National
PC16552 and Exar’s XR16L2752 and XR16C2852
4 Mbps transmit/receive operation (64 MHz
External Clock Frequency)
2 Independent UART Channels
■ Register Set Compatible to 16C550
■ 16 byte Transmit FIFO to reduce the bandwidth
requirement of the external CPU
■ 16 byte Receive FIFO with error tags to reduce
the bandwidth requirement of the external CPU
■ 4 selectable RX FIFO Trigger Levels
■ Fixed Transmit FIFO interrupt trigger level
■ Full Modem Interface (CTS#, RTS#, DSR#,
DTR#, RI#, CD#)
DMA operation and DMA monitoring via TXRDY#
and RXRDY# pins
UART internal register sections A & B may be
written to concurrently
Multi-Function output allows more package
functions with few I/O pins
Programmable character lengths (5, 6, 7, 8) with
even, odd, or no parity
Crystal oscillator or external clock input
FIGURE 1. ST16C2552 BLOCK DIAGRAM
MFA#
(OP2A#,
BAUDOUTA#, or
RXRDYA#)
MFB#
(OP2B#,
BAUDOUTB#, or
RXRDYB#)
XTAL1
XTAL2
Crystal Osc/Buffer
TXA (or TXIRA)
8-bit Data
Bus
Interface
UART Channel A
16 Byte TX FIFO
16 Byte RX FIFO
BRG
TX & RX
UART
Regs
3.3V or 5V VCC
GND
2552BLK
UART Channel B
(same as Channel A)
A2:A0
D7:D0
CS#
CHSEL
INTA
INTB
IOW#
IOR#
Reset
TXRDYA#
TXRDYB#
CTS#A/B, RI#A/B,
CD#A/B, DSR#A/B
RXA (or RXIRA)
Modem Control Logic
DTR#A/B, RTS#A/B
TXB (or TXIRB)
RXB (or RXIRB)