MOTOROLA
Chapter 5. System Design Considerations
5-3
Standby Mode
The expected duration of each step in the startup sequence is shown in Table 5-2. A cold
startup can be initiated at any time by negating RESET low. It is recommended that RESET
be low at initial startup, but, it is not strictly required.
5.3
Standby Mode
Standby mode puts the MC92603 into a low power, inactive state. When STNDBY is
asserted high, the device will force all transmitter link outputs to their disabled state as
defined in Section 2.3.1, “Transmit Driver Operation,” and disables all internal clocking.
An important feature of standby mode is that the internal PLL is not disabled. It remains
operating and locked to the reference clock. This greatly reduces the time needed to recover
from standby mode to run mode, as only the receiver initialization and word alignment
startup steps are required.
5.4
Receiver Interface Clock Centering
All interface output drivers are internally source terminated with 50
Ω
. Therefore, no
external source terminations are required.
The receiver interface also has the option of having the output data source-aligned or
source-centered with the respective channel RECV_x_CLK. If source-aligned, then the
considerations for pcb design must include lengthening the clock trace to meet interface
setup time requirements. However, the suggested method would be to use the
source-centered option to maximize the setup and hold times, keeping the clock and data
traces the same length. This applies for all modes of operation (backplane or Ethernet
compatibility and normal or reduced interface modes). For more information, see
Section 3.6, “Receiver Interface Timing Modes,” and the specifications in Section 7.3.2,
“Receiver Interface Timing.”
Table 5-2. Startup Sequence Step Duration
Startup Step
Typical Duration
(in Bit Times)
Notes
PLL startup
20480 + 25
µ
s
Receiver initialization
300
WSYNC1 and WSYNC0 = low
Word alignment
160
WSYNC1 or WSYNC0 = high
Summary of Contents for MC92603
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