Datasheet

TL16C554A, TL16C554AI
ASYNCHRONOUS-COMMUNICATIONS ELEMENT
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SLLS509E − AUGUST 2001 − REVISED JUNE 2010
32
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Table 12. Baud Rates Using an 16-MHz Clock
BAUD RATE
DESIRED
DIVISOR (N) USED TO
GENERATE 16 × CLOCK
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
50 20000 0
75 13334 0.00
110 9090 0.01
134.5 7434 0.01
150 6666 0.01
300 3334 −0.02
600 1666 0.04
1200 834 −0.08
1800 554 0.28
2000 500 0.00
2400 416 0.16
3600 278 −0.08
4800 208 0.16
7200 138 0.64
9600 104 0.16
19200 52 0.16
38400 26 0.16
56000 18 −0.79
128000 8 −2.34
256000 4 −2.34
512000 2 −2.34
1000000 1 0.00
receiver
Serial asynchronous data is input into the RXx terminal. The ACE continually searches for a high-to-low
transition. When the transition is detected, a circuit is enabled to sample incoming data bits at the optimum point,
which is the center of each bit. The start bit is valid when RXx is still low at the sample point. Verifying the start
bits prevents the receiver from assembling a false data character due to a low-going noise spike on the RXx
input.
The number of data bits in a character is controlled by LCR0 and LCR1. Parity checking, generation, and polarity
are controlled by LCR3 and LCR4. Receiver status is provided in the LSR. When a full character is received,
including parity and stop bits, the data received indicator in LSR0 is set. In non-FIFO mode, the CPU reads the
RBR, which clears LSR0. If the character is not read prior to a new character transfer from RSR to RBR, an
overrun occurs and the overrun error status indicator is set in LSR1. If there is a parity error, the parity error is
set in LSR2. If a stop bit is not detected, a framing error indicator is set in LSR3.
In the FIFO mode, the data character and the associated error bits are stored in the receiver FIFO. If the data
in RXx is a symmetrical square wave, the center of the data cells occurs within ±3.125% of the actual center,
providing an error margin of 46.875%. The start bit can begin as much as one 16× clock cycles prior to being
detected.