NS16C2552 Datasheet, PDF (5/50 Pages) National Semiconductor (TI) – Dual UART with 16-byte/64-byte FIFOs and up to 5 Mbit/s Data Rate

NS16C2552, NS16C2752
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Signal
Name
RI1
RI2
Type
I
MF1
O
MF2
PLCC
Pin #
43
31
35
19
SNLS238D – AUGUST 2006 – REVISED APRIL 2013
TQFP
Pin #
41
27
32
14
Description
UART Ring-detector:
When low, RI indicates that a telephone ringing is active. The RI signal is a MODEM status input
and can be read for the appropriate channel in MSR[6]. This bit reflects the complement of the RI
signal. MSR[2] indicates whether the RI input signal has changed state from low to high since the
previous reading of the MSR.
Note: Whenever the RI bit of the MSR changes from a high to a low state, an interrupt is
generated if the MODEM Status Interrupt is enabled.
UART Multi-function Pin:
MF can be programmed for any one of three signal functions OUT2, BAUDOUT or RXRDY. Bits 2
and 1 of the Alternate Function Register select which output signal will be present on this pin.
OUT2 is the default signal and it is selected immediately after master reset or power-up.
The OUT2 can be set active low by programming bit 3 (OUT2) of the MCR to a logic 1. A Master
Reset operation sets this signal to its inactive (high) state. Loop Mode holds this signal in its
inactive state.
The BAUDOUT signal is the 16X clock output that drives the transmitter and receiver logic of the
associated serial channel. This signal is the result of the XIN clock divided by the value in the
Divisor Latch Registers. The BAUDOUT signal for each channel is internally connected to provide
the receiver clock (formerly RCLK on the PC16550D).
The RXRDY signal can be used to request a DMA transfer of data from the RCVR FIFO. Details
regarding the active and inactive states of this signal are described in FIFO CONTROL
REGISTER (FCR) and DMA OPERATION.
CLOCK AND RESET
Signal
Name
XIN
Type
I
PLCC
Pin #
11
XOUT
O
13
MR
I
21
TQFP
Pin #
5
7
16
Description
External Crystal Input:
XIN input is used in conjunction with XOUT to form a feedback circuit for the baud
rate generator's oscillator. If a clock signal is generated off-chip, then it should drive
the baud rate generator through this pin. Refer to CLOCK INPUT.
External Crystal Output:
XOUT output is used in conjunction with XIN to form a feedback circuit for the baud
rate generator's oscillator. If the clock signal is generated off-chip, then this pin is
unused. Refer to CLOCK INPUT.
Master Reset:
When MR input is high, it clears all the registers including Tx and Rx serial shift
registers (except the Receiver Buffer, Transmitter Holding, and Divisor Latches). The
output signals, such as OUT2, RTS, DTR, INTR, and SOUT are also affected by an
active MR input. (Refer to Table 26 and RESET).
POWER AND GROUND
Signal
Name
VCC
GND
NC
Type
I
I
I
PLCC
Pin #
33
44
12
22
N/A
TQFP
Pin #
29
42
6
17
19
37
Description
V_CC:
+2.97V to +5.5V supply.
GND:
Device ground reference.
No Connection:
These pins are only available on the TQFP package.
Copyright © 2006–2013, Texas Instruments Incorporated
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