DAN-170 Datasheet, PDF (2/7 Pages) Exar Corporation – MIGRATING TO EXAR’S FIFTH GENERATION UARTS

DATA COMMUNICATIONS APPLICATION NOTE
DAN170
TABLE 1: HARDWARE DIFFERENCES BETWEEN ONE ST16C454/554/654/854/864 AND ONE XR16L784
DESCRIPTION
ONE ST16C454/554/654/854/864
ONE XR16L784
Footprint
5V Tolerant inputs (when VCC < 5V)
Chipselect
Interrupt
Address Lines
68-PLCC, 64-TQFP or 100-QFP
64-TQFP
Not Available
Yes
One chipselect per channel*
(requires external address decoder
logic to generate the 4 chipselects)
One chipselect for the entire chip
One active Interrupt per channel*
(cannot be wire-ORed; requires
external logic to combine the 4
interrupts into a single IRQ)
One open-drain interrupt for the entire chip
(can be wire-ORed)
3 (A2:A0) for 8 registers (and 7 8 lines (A7:A0) for 16 registers per channel
shadow registers)
and 15 Device Configuration registers for the
entire device)
TABLE 2: HARDWARE DIFFERENCES BETWEEN TWO ST16C454/554/654/854/864’S AND ONE XR16L788
DESCRIPTION
TWO ST16C454/554/654/854/864
ONE XR16L788
Footprint
Two
68-PLCC, 64-TQFP or 100-QFP
One 100-QFP
5V Tolerant inputs (when VCC < 5V)
Chipselect
Not Available
One chipselect per channel*
(requires external address decoder
logic to generate the 8 chipselects)
Yes
One chipselect for the entire chip
Interrupt
Address Lines
One active Interrupt per channel*
(cannot be wire-ORed; requires
external logic to combine the 8
interrupts into a single IRQ)
One open-drain interrupt for the entire chip
(can be wire-ORed)
3 (A2:A0) for 8 registers (and 7 8 lines (A7:A0) for 16 registers per channel
shadow registers)
and 15 Device Configuration registers for the
entire device)
*Note that these differences are only when the device operates in Intel mode (16/68# pin is HIGH). In Motorola
mode (16/68# pin is LOW), each ST16C454/554/654/854/864 device has only one chipselect (with two addi-
tional address lines to select the four channels) and one open-drain interrupt output, similar to the XR16L784.
However, when using two of the ST16C454/554/654/854/864’s, one extra chipselect is still required, compared
to the XR16L788.
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