DATA COMMUNICATIONS APPLICATION NOTE

DAN138

7

1.4

You can directly replace TI’s TL16C752B with Exar’s XR16L2550 with minimal hardware changes if using the

48-LQFP package. Also, you can replace the TL16C752B with the XR16L2551 if the two extra input pins are

tied to GND or VCC appropriately as discussed in Table 2. The crystal oscillator circuitry will work in most cas-

es, but it may be necessary to modify the oscillator circuitry as well.

The software may need to be updated if the existing design is using the Halt and Resume Transmission Levels

of the TL16C752B since the XR16L2550 and XR16L2551 do not have that feature. Software updates are also

needed if infrared mode of the Exar 2-channel UARTs are used since that feature is not available in the

TL16C752B.

The TL16C752B is a 3.3 V device only, but can be replaced by any of the Exar 2-channel UARTs because they

can operate from 2.25 V to 5.5 V. At any voltage, the Exar 2-channel UARTs have a lower power consumption

than the TL16C752B.

There should not be any timing problems replacing the TL16C752B with the Exar 2-channel UARTs because

they are more flexible than the TL16C752B as described in the bus timing section.

1.5

The TL16C752B has two known deficiencies and are directly stated in TI’s datasheet.

On page 12 of the TL16C752B’s datasheet dated “December 1999 - Revised August 2000,” TI gives a note ad-

vising not to write to Baud Rate Divisors DLL and DLH (DLM) while in sleep mode. Exar 2-channel UARTs do

not have any such problems.

On page 22 of the TL16C752B datasheet, they describe a “timing error condition” in non-FIFO mode where the

LSR and IIR (ISR) reports a data byte as available to read from the RHR, but there is no valid data ready to be

read from the RHR. The Exar 2-channel UARTs do not have this problem in FIFO or non-FIFO mode.