QT2022/32 - Data Sheet: DS3051
Table 31: TXENABLE Logic (XFP = 1)
x
1
x
x
x
0
x
x
1
x
x
0
x
x
x
1
x
0
x
x
x
x
1
0
Disabled
Disabled
Disabled
Disabled
Disabled
Enabled
Float
Float
Float
Float
Float
Low
8.5 Low-Speed Output Pins (QT2032 only)
The pins described in this section apply to the QT2032 only. These pins are not defined for the QT2022 product.
All the low-speed output pins have the same type of open drain driver. An external 10-22kΩ pullup resistor to 1.2V
is expected. The open drain configuration allows these signals to be wire or’ed with other active low open drain dis-
able signals on the module. There are no internal pullups or pulldowns on these pins.
8.5.1 Line Timing Okay Status Pin (LTIMEOK)
The LTIMEOK pin is used in a WAN application using line timing mode where an external VXCO PLL circuit has
been implemented and a fixed reference is not provided on SREFCLK, as explained in Section 6.2.4, “VCXO PLL,”
on page 32. The LTIMEOK pin is to be used to force the external VCXO to its center frequency when line timing
conditions are not valid or line timing is disabled. When linetiming conditions are valid and linetiming is enabled, a
logic HIGH on LTIMEOK indicates that the VCXO may lock to the Fiber RX recovered clock. When linetiming con-
ditions are not valid or linetiming is disabled, a logic low on the LTIMEOK output pin will force the VCXO to its
center frequency.
Refer to Section 6.2.4, “VCXO PLL,” on page 32 for detailed information on the operation of the VCXO PLL.
8.6 LED/GPIO Driver Pins (LEDx)
The QT2022/32 incorporates three bidirectional I/Os. One of the primary applications for these pins is as direct
LED drivers in hostboard applications. They can also be used for general purpose input or output.
Each LED driver may be programmed to one of several different modes using the LED Configuration Registers
1.D006h, 1D007h and 1.D008h (for LED1, LED2 and LED3 respectively).
Each LED can be programmed to indicate one of the following conditions:
•
•
•
•
•
RX or TX Link Status Only
RX or TX Activity Status Only
RX or TX Link Status/Activity Status Combined
LED on
LED off
70
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