DATA COMMUNICATIONS APPLICATION NOTE

DAN121

2

1.4

In the table below, some differences between the XR68C92/192 and SCC68692 are summarized.

1.5

You can directly replace the Philips SCC68692 with Exar’s XR68C92/192 without any hardware changes if us-

ing either the 44-PLCC or 40-PDIP packages. Hardware changes will be necessary to upgrade to the smaller

44-TQFP package.

Since the XR68C92/192 has a larger Transmit and Receive FIFO, the software will need to be updated to fully

utilize the features of the XR68C92/192. The XR68C92/192 allows the hardware designer to choose either a 5

or 3.3 V power supply instead of being limited to a 5 V power supply only. Also, the XR68C92/192 has a lower

power consumption than the SCC68692.

The XR68C92/192 can accept up to a 24 MHz frequency on XTAL1 whereas the SCC68692 can only accept

up to a 4 MHz frequency. The maximum data transfer rate for the XR68C92/192 is 1 Mbps compared to only

125 Kbps for the SCC68692.

XR68C92/192

SCC68692

Data Bus Standard

Motorola

Motorola

Power Supply Operation

3.3 and 5 V

5 V only

Max Operating Current

3 mA @ 3.3 V

6 mA @ 5 V

10 mA @ 5 V

Max Frequency on XTAL1

24 MHz

4 MHz

Max Data Rate

1 Mbps

125 Kbps

Operating Temperature Range

Commercial and Industrial

Commercial and Industrial

Package

44-TQFP, 44-PLCC,

40-PDIP

44-PLCC, 40-PDIP,

40-CDIP

TX FIFO Size

8 (XR68C92)

16 (XR68C192)

1

RX FIFO Size

8 (XR68C92)

16 (XR68C192)

3

TX FIFO Trigger Levels

8, 4, 6, 1 (XR68C92)

16, 8, 12, 1(XR68C192)

1

RX FIFO Trigger Levels

1, 3, 6, 8 (XR68C92)

1, 6, 12, 16 (XR68C192)

1, 3