SC16C550B All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 6 — 16 December 2014 8 of 49
NXP Semiconductors
SC16C550B
5 V, 3.3 V and 2.5 V UART with 16-byte FIFOs
RI
[2]
43 41 39 27 I Ring indicator. RI is a modem status signal. Its condition
can be checked by reading bit 6 (RI
) of the Modem Status
Register. Bit 2 (RI) of the Modem Status Register
indicates that RI has changed from a LOW to a HIGH level
since the last read from the Modem Status Register. If the
modem status interrupt is enabled when this transition
occurs, an interrupt is generated.
RTS
36 32 32 21 O Request to send. When active, RTS informs the modem
or data set that the UART is ready to receive data. RTS
is
set to the active level by setting the RTS
Modem Control
Register bit and is set to the inactive (HIGH) level either as
a result of a Master Reset or during loopback mode
operations or by clearing bit 1 (RTS
) of the MCR. This pin
has no effect on the UART’s transmit or receive operation.
RXRDY
32 29 29 - O Receiver ready. Receiver Direct Memory Access (DMA)
signaling is available with RXRDY
. When operating in the
FIFO mode, one of two types of DMA signaling can be
selected using the FIFO Control Register bit 3 (FCR[3]).
When operating in the 16C450 mode, only DMA mode 0 is
allowed. Mode 0 supports single-transfer DMA in which a
transfer is made between CPU bus cycles. Mode 1
supports multi-transfer DMA in which multiple transfers are
made continuously until the receiver FIFO has been
emptied. In DMA mode 0 (FCR[0] = 0 or FCR[0] = 1,
FCR[3] = 0), when there is at least one character in the
receiver FIFO or Receiver Holding Register, RXRDY
is
active (LOW). When RXRDY
has been active but there are
no characters in the FIFO or holding register, RXRDY goes
inactive (HIGH). In DMA mode 1 (FCR[0] = 1, FCR[3] = 1),
when the trigger level or the time-out has been reached,
RXRDY
goes active (LOW); when it has been active but
there are no more characters in the FIFO or holding
register, it goes inactive (HIGH). This function does not
exist in the HVQFN32 package.
RX 11 7 10 6 I Serial data input. RX is serial data input from a connected
communications device.
TX 13 8 11 7 O Serial data output. TX is composite serial data output to a
connected communication device. TX is set to the marking
(HIGH) level as a result of Master Reset.
TXRDY
27 23 24 - O Transmitter ready. Transmitter DMA signaling is available
with TXRDY
. When operating in the FIFO mode, one of
two types of DMA signaling can be selected using FCR[3].
When operating in the 16C450 mode, only DMA mode 0 is
allowed. Mode 0 supports single-transfer DMA in which a
transfer is made between CPU bus cycles. Mode 1
supports multi-transfer DMA in which multiple transfers are
made continuously until the transmit FIFO has been filled.
This function does not exist in the HVQFN32 package.
V
DD
44 42 40 28 power 2.5V, 3.3V or 5V supply voltage.
V
SS
22 18 20 9, 13
[1]
power Ground voltage.
Table 2. Pin description
…continued
Symbol Pin Type Description
PLCC44 LQFP48 DIP40 HVQFN32
