Datasheet

1.0 Pin Descriptions (Continued)
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1.3 Clock Interface
1.4 Device Configuration Interface
Signal Name Type Pin # Description
X1 I 9 CRYSTAL/OSCILLATOR INPUT: This pin is the primary clock reference input for
the DP83843 and must be connected to a 25 MHz 0.005% (50 ppm) clock source.
The DP83843 device supports either an external crystal resonator connected across
pins X1 and X2, or an external CMOS-level oscillator source connected to pin X1
only. For 100 Mb/s repeater applications, X1 should be tied to the common 25 MHz
transmit clock reference. Refer to section 4.4 for further detail relating to the clock
requirements of the DP83843. Refer to section 4.0 for clock source specifications.
X2 O 8 CRYSTAL/OSCILLATOR OUTPUT PIN: This pin is used in conjunction with the X1
pin to connect to an external 25 MHz crystal resonator device. This pin must be left
unconnected if an external CMOS oscillator clock source is utilized. For more infor-
mation see the definition for pin X1. Refer to section 2.8 for further detail.
Signal Name Type Pin # Description
AN0 I
(3-level)
4 AN0: This is a three level input pin (1, M, 0) that works in conjunction with the AN1
pin to control the forced or advertised operating mode of the DP83843 according to
the following table. The value on this pin is set by connecting the input pin to GND
(0), V
CC
(1), or leaving it unconnected (M.) The unconnected state, M, refers to the
mid-level (V
CC
/2) set by internal resistors. The value set at this input is latched into
the DP83843 at power-up/reset.
AN1 I
(3-level)
3 AN1: This is a three-level input pin (i.e., 1, M, 0) that works in conjunction with the
AN0 pin to control the forced or advertised operating mode of the DP83843 accord-
ing to the table given in the AN0 pin description above. The value on this pin is set
by connecting the input pin to GND (0), V
CC
(1), or leaving it unconnected (M.) The
value at this input is latched into the DP83843 at power-up, hardware or software
reset.
AN1 AN0 Forced Mode
0 M 10BASE-T, Half-Duplex without Auto-Negotiation
1 M 10BASE-T, Full Duplex without Auto-Negotiation
M 0 100BASE-X, Half-Duplex without Auto-Negotiation
M 1 100BASE-X, Full Duplex without Auto-Negotiation
AN1 AN0 Advertised Mode
M M All capable (i.e. Half-Duplex & Full Duplex for 10BASE-T and
100BASE-TX) advertised via Auto-Negotiation
0 0 10BASE-T, Half-Duplex & Full Duplex advertised via Auto-
Negotiation
0 1 100BASE-TX, Half-Duplex & Full Duplex advertised via
Auto-Negotiation
1 0 10BASE-T & 100BASE-TX, Half-Duplex advertised via Auto-
Negotiation
1 1 10 BASE-T, Half-Duplex advertised via Auto-Negotiation