XR68C681 Datasheet, PDF (10/75 Pages) Exar Corporation – CMOS Dual Channel UART (DUART)

XR68C681
AC ELECTRICAL CHARACTERISTICS ^{1, 2, 3} (CONT’D)
Test Conditions: TA = 0 - 70
C, VCC = 5.0V +5% unless otherwise specified.
Symbol Parameter
Min
Typ
Max
Unit Conditions
Clock Timing (Figure 38)
5
5
 $ 5
2!  9(- 

: ( ^<
+5
5
 $ 5
2!  C '&
/5

5

Transmitter Timing (Figure 39)
5
5  &  5
2! 
:


5  &  5
#  
 :
Receiver Timing (Figure 40)
5
5   (  5

=
2!  9(-
59
5  9$ ( + 5


2!  9(-
%
/
9G

9G
16
%
6
%
%
%
Notes
1._{Parameters are valid over the specified temperature and operating supply ranges. Typical values are 25
C, VCC = 5V and typical}
processing parameters.
2._{All voltages are referenced to ground (GND). For testing, input signal levels are 0.4V and 2.4V with a transition time of 20ns}
maximum. All time measurements are referenced at input voltages of 0.8V and 2.0V as appropriate. See Figure 31.
3._{AC test conditions for outputs: CL = 50pF, RL = 2.7k• to VCC.}
4._{Consecutive write operations to the same register require at least three edges of the X1 clock between writes.}
5._{This specification imposes a 6 MHz maximum 68000 clock frequency if a read or write cycle follows immediately after the previous}
read or write cycle. A higher 68000 clock can be used if this is not the case.
6._{This specification imposes a lower bound on CS and IACK low, guaranteeing that they will be low for at least one CLK period.}
7._{This parameter is specified only to insure DTACK is asserted with respect to the rising edge of X1/CLK as shown in the timing dia-}
gram, not to guarantee operation of the part. If the specified setup time is violated, DTACK may be asserted as shown or may be
asserted one clock cycle later.
8._{The minimum high time must be at least 1.5 times the X1/CLK period and the minimum low time must be at least equal to the X1/CLK}
period if either channel’s Receiver is operating in external 1X clock mode.
Specifications are subject to change without notice
ABSOLUTE MAXIMUM RATINGS¹

& ;-                          @;
-               /6

 6


 ;-% ( %'  0 $^    6;  ?@;
1._{Stresses above those listed under the Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rat-}
ing only, and functional operation of the device at these or any other conditions above those indicated in the “Electrical Characteris-
tics” section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
2._{This product includes circuitry specifically designed for the protection of its internal devices from damaging effects of excessive stat-}
ic charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying any voltage larger than the rated
maximum.