Figure 674. Example Of Sleep Mode - STMicroelectronics SPC572L series Reference Manual

LVDS Fast Asynchronous Serial Transmission (LFAST) – Interprocessor Communications
time is required before the LD may be used for communication.The settling time is
defined by the SLCR[LWKCNT] and SLCR[HWKCNT] bitfields.
•
Sleep
The LD enters in sleep state when the signal is asserted. In this state, the LD is
enabled, but held in a power-saving state. Sleep mode may be used during inter-frame
gaps that are long compared to the frame durations but not long enough to allow the
interface(s) or high-speed clock generators to be powered down completely. In the
sleep state the LD outputs are connected to Vcm (common mode voltage). To exit from
Sleep mode the LD sleep signal is negated. The LD is required to transmit a logic 0
level on the interface for a predefined minimum time. The minimum time is the
summation of settling time of LD after negation of LD sleep signal and the wakeup time
of the LR on the other side. This delay is programed in the SLCR[HSCNT] and
SLCR[LSCNT] bitfields.
Normal mode
120mV
120mV
1 after Frame indicates Sleep mode
Line Receiver turns off designated circuitry
As shown in
guard bit period (minimum inter-frame gap) where a logic 0 will be transmitted.
•
Normal
In the Normal state the LD is primed for transmission. The LD shall drive the interface
as dictated by the input data bit that is supplied by a shift register under the control of a
finite state machine. If the LD is not enabled, and the framer is activated, and has a
frame to transmit, an interrupt (TISR[TXIEF]) will be generated. The LD moves back to
the shutdown state when the LFAST master sends an ICLC Rx data off command.
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Figure 674. Example of Sleep mode

Logic 1
After Frame
Sleep mode
00000000b for High Speed
OR
0 for Low Speed
Figure 674 before every normal mode burst on the txdatap line there is one
DocID027809 Rev 4
Normal mode
0
Guard Bit
Normal mode
120mVpkd
Assuming a differential voltage swing
of +/- 120 or 240mVpk-pk in this example
CM (1.2V)