Datasheet

TL16C2550

SLWS161E –JUNE 2005–REVISED NOVEMBER 2012

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PIN FUNCTIONS (continued)

I/O DESCRIPTION

NAME PFB FN RHB

Request to send (active low). These outputs are associated

with individual UART channels A and B. A low on the RTS pin

indicates the transmitter has data ready and waiting to send.

Writing a 1 in the modem control register (MCR bit 1) sets

RTSA, RTSB 33, 22 36, 27 23, 15 O these pins to low, indicating data is available. After a reset,

these pins are set to high. These pins only affects the

transmit and receive operation when auto RTS function is

enabled through the enhanced feature register (EFR) bit 6,

for hardware flow control operation.

Receive data input. These inputs are associated with

individual serial channel data to the 2550. During the local

RXA, RXB 5, 4 11, 10 4, 3 I

loopback mode, these RX input pins are disabled and TX

data is internally connected to the UART RX input internally.

Receive ready (active low). RXRDY A and B goes low when

the trigger level has been reached or a timeout interrupt

RXRDYA, RXRDYB 31, 18 34, 23 – O

occurs. They go high when the RX FIFO is empty or there is

an error in RX FIFO.

Transmit data. These outputs are associated with individual

serial transmit channel data from the 2550. During the local

TXA, TXB 7, 8 13, 14 5 , 6 O

loopback mode, the TX input pin is disabled and TX data is

internally connected to the UART RX input.

Transmit ready (active low). TXRDY A and B go low when

TXRDYA, TXRDYB 43, 6 1, 12 – O there are at least a trigger level numbers of spaces available.

They go high when the TX buffer is full.

42 44 26 I Power supply inputs.

Crystal or external clock input. XTAL1 functions as a crystal

input or as an external clock input. A crystal can be

connected between XTAL1 and XTAL2 to form an internal

XTAL1 13 18 10 I

oscillator circuit (see Figure 14). Alternatively, an external

clock can be connected to XTAL1 to provide custom data

rates.

Output of the crystal oscillator or buffered clock. See also

XTAL2 14 19 11 O XTAL1. XTAL2 is used as a crystal oscillator output or

buffered a clock output.

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