MAX9257GTL+ Maxim Integrated Products, MAX9257GTL+ Datasheet - Page 29

• Manufacturer Part Number: MAX9257GTL+
• Description: IC SER/DESER PROG 40-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX9257GTL+

• Function: Serializer/Deserializer
• Data Rate: 840Mbps
• Input Type: Serial
• Output Type: LVDS
• Number Of Inputs: 16
• Number Of Outputs: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

counter bits REG3[3:0] that increment once every ETO
clock period. Write to REG3[3:0] to determine the
counter end time. The ETO counter counts to the pro-
grammed ETOCNT + 1. Any ECU activity resets the
ETO timer. When the ECU stops transmitting data for
the ETO timeout period, the control channel closes
(Figure 23).
For example:
If the pixel clock frequency is set to 16MHz, ETODIV is
set to 1010 (ETODIV = 1024), and ETOCNT is set to
1001 (ETOCNT = 9), the ETO timer counts with the
15.625kHz ETO clock (16MHz/1024) internally until it
reaches 10 and timer expires. The t
1024 x 10 = 640µs.
The default value for ETODIV is 1024 while the default
value for ETOCNT is 0. That means the ETO timeout
period is equal to 1,024 pixel clock cycles.
After the MAX9257 detects the active VSYNC edge, it
sends three synchronization words. Once the MAX9258
sees the active VSYNC transition and detects three syn-
chronization words, it enters the control channel phase
and CCEN goes high. There is a brief delay of T1
Figure 23. Control Channel Closing Due to ETO Timeout
t
ETO
Fully Programmable Serializer/Deserializer
=
⎛
⎜
⎝
VSYNC_IN
f
CLK
______________________________________________________________________________________
SDI/O±
DOUT_
1
T1 = TIME TO ENTER CONTROL CHANNEL
T4 = ETO TIMEOUT PERIOD
T5 = CONTROL CHANNEL EXIT TIME DUE TO ETO
HSK = HANDSHAKING BETWEEN MAX9257 AND MAX9258
CCEN
TX
RX
⎞
⎟ ×
⎠
ETODIV
Closing the Control Channel
VIDEO
×
(
ETOCNT
T1
ETO
is equal to t
with UART/I
+
1
)
ACTIVITY
ECU
T
x
FROZEN
between the VSYNC transition and CCEN transitioning
high. The ECU is allowed to communicate when CCEN
is high.
If the ECU does not communicate while CCEN is high
(Figure 22), the link remains silent and STO starts
counting towards its preset timeout counter value. If
STO times out (T2), CCEN transitions low and the con-
trol channel closes.
If the ECU communicates while CCEN is high and
before STO expires (Figure 23), the STO timer is turned
off and ETO timer is enabled. The ETO counter (ETOC-
NT+1) is reset to 0 whenever activity from ECU (base
mode) or ECU and Camera (bypass mode) is detected.
As long as there is activity from ECU (base mode) or
ECU and Camera (bypass mode) on the link, the chan-
nel does not close and the ETO counter resets. After
the ECU (base mode) or ECU and Camera (bypass
mode) ceases link activity, ETO times out (T4), CCEN
transitions low, and the control channel closes.
Another way to close the control channel in base mode
is for the ECU to send an end frame (EF) to close the
control channel without waiting for ETO to time out.
Whenever EF is received by both the MAX9257/
MAX9258, control channel closes immediately and
CCEN goes low. A synchronization frame must precede
EF. End frame cannot be used in bypass mode. The
control channel must close by EF to report errors back
to the ECU.
T4 (BASE MODE)
T4 (BYPASS MODE)
2
C Control Channel
T5
HSK
VIDEO
29