Table 12: GTM Transceiver Reset Modes Ports
Port
Direction
Clock Domain
Description
CH[0/1]_RXRESETMODE[1:0]
In
Async
Reset mode port for RX.
2'b00
: Sequential mode
(recommended).
2'b01
: Reserved.
2'b10
: Reserved.
2'b11
: Single mode.
CH[0/1]_TXRESETMODE[1:0]
In
Async
Reset mode port for TX.
2'b00
: Sequential mode
(recommended).
2'b01
: Reserved.
2'b10
: Reserved.
2'b11
: Single mode.
LCPLL Reset
The LCPLL must be reset before it can be used. Each GTM transceiver dual has dedicated reset
ports for its LCPLL. As shown in the figure, PLLRESET is an input that resets LCPLL. PLLLOCK is
an output that indicates the reset process is done. The guideline for this asynchronous PLLRESET
pulse width is one period of the reference clock. After a PLLRESET pulse, the internal reset
controller generates an internal LCPLL reset followed by an internal SDM reset. The time
required for LCPLL to lock is affected by a few factors, such as bandwidth setting and clock
frequency.
Figure 12:
LCPLL Reset Timing Diagram
Table 13: LCPLL Reset Ports
Port
Dir
Clock
Domain
Description
PLLRESET
In
Async
Active-High signal that resets the LCPLL.
PLLRESETMASK[1:0]
In
Async
Reserved. Tied to
2’b11
.
PLLRESETBYPASSMODE
In
Async
Reserved. Tied Low.
PLLLOCK
Out
Async
Active-High LCPLL frequency lock signal indicates that the
LCPLL frequency is within a predetermined tolerance. The
GTM transceiver and its clock outputs are not reliable until
this condition is met.
Chapter 2: Shared Features
UG581 (v1.0) January 4, 2019
Virtex Ult GTM Transceivers
26