AMD
multiplier is switched out, and the internal logic is
clocked directly from the CLK pin. Test Mode 2 is in-
cluded to ease Automatic Test Equipment (A.T.E.) test-
ing by making the internal logic of the Transmitter
synchronous to the external clock instead of the
internal PLL.
X1, X2
Crystal Oscillator Inputs (Inputs)
The two crystal input pins connect to an internal parallel
mode oscillator which operates at the fundamental fre-
quency of the external crystal. The byte rate matches
the crystal frequency. During normal operation, the byte
rate is set by the crystal frequency.
Alternatively, X1 can be driven by an external TTL fre-
quency source. In multiple TAXI systems this external
source could be another Am7968’s CLK output.
TSERIN
Test Serial Input (Pseudo ECL Input)
This pin is left unconnected in Local Mode operation.
TSERIN can be used to input serial data patterns into
the Shifter in Test Mode 1 operation.
V
CC1
, V
CC2
, V
CC3
Power Supply
V
CC1
,
V
CC2
, and V
CC3
are +5.0 volt nominal power sup-
ply pins. V
CC1
powers TTL I/O, V
CC2
powers ECL and
V
CC3
powers internal Logic and Analog circuitry.
Am7968/Am7969
7
AMD [ ADVANCED MICRO DEVICES ]
