DAN-123 Datasheet, PDF (1/3 Pages) Exar Corporation – EXAR’S XR88C92/192 COMPARED

DATA COMMUNICATIONS APPLICATION NOTE
DAN123
June 2002
EXAR’S XR88C92/192 COMPARED WITH PHILIP’S SCC2692
Author: PY
1.0 INTRODUCTION
This application note describes the major difference between Exar’s XR88C92/192 with Philips’s SCC2692.
These devices are very similar, with a few hardware, firmware-related and bus timing differences.
1.1 HARDWARE DIFFERENCES
• The Philips SCC2692 and Exar XR88C92/192 are both available in three footprints: 44-pin PLCC, 44-pin
QFP and 40-pin DIP. Additionally, the SCC2692 is also available in a 28-pin DIP. In the PLCC, QFP and 40-
DIP packages, the Exar and Philips DUARTs are pin-to-pin compatible.
• The Exar’s 44-pin TQFP package is the same size and has the same pitch as the Philips’ 44-pin QFP pack-
age. But they differ in the package thickness and the lead length. See the list below:
Thickness:
Lead Length, Lp:
Exar
1.4mm
0.45mm < Lp < 0.75mm
Philips
1.75mm
0.55mm < Lp < 0.95mm
1.2 FIRMWARE DIFFERENCES
All the internal registers in the SCC2692 and XR88C92/192 are identical with only a few exceptions:
• The XR88C92/192 has an additional mode register, Mode Register 0 (Watch dog timer, RX and TX trigger
levels and extended baud rate tables), for channels A and B while the SCC2692 does not.
• Since the XR88C92/192 has a larger FIFO than the SCC2692, the selectable transmit and receive trigger
levels are different.
• At the address offset of 0x2 and 0xA, the SCC2692 has a read-only BRG Test Register and 1X/16X Test
Register, respectively, while these offsets are reserved for the XR88C92/192.
• The XR88C92/192 has a Miscellaneous Command in the CRA and CRB register bits 7-4 that has a different
function than the SCC2692. When 0xB is written to the upper nibble of CRA or CRB, the XR88C92/192 sets
the MR pointer to MR0, but this has no effect on the SCC2692.
1.3 BUS TIMING DIFFERENCES
• The XR88C92/192 is faster than the SCC2692. For example, the data access time (from -CS low to data
valid) during a read is a maximum of 32 ns for the XR88C92/192, whereas it is a maximum of 175 ns for the
SCC2692.
EXAR Corporation 48720 Kato Road, Fremont CA, 94538 • [phone] • FAX [phone] • www.exar.com • [e-mail]