max9257agcm/v+ Maxim Integrated Products, Inc., max9257agcm/v+ Datasheet - Page 33

• Manufacturer Part Number: max9257agcm/v+
• Description: Fully Programmable Serializer/deserializer With Uart/i2c Control Channel
• Manufacturer: Maxim Integrated Products, Inc.

sends three special synchro nization words before enter-
ing the video phase. Training sequence is used to resyn-
chronize the devices before the video phase starts.
The MAX9257A/MAX9258A control channel duration is
independent of VSYNC. The control channel does not
close when VSYNC deasserts, which allows the use
of a VSYNC interrupt signal on VSYNC_IN. The control
channel must be closed by STO, ETO, or EF. If the con-
trol channel does not close before video data becomes
available, video data can be lost.
STO and ETO can be programmed given the values of
T2, T4, and maximum values of T1, T3, and T5
28, 23):
When pixel clock frequency range (PRATE) is 00 or 01:
When pixel clock frequency range (PRATE) is 10 or 11:
The CTO (come-back timeout) timer temporarily or
per manently blocks programming to the MAX9257A/
MAX9258A registers. CTO keeps the devices in bypass
mode for the CTO timeout period
mode can only be exited when the CTO timer expires.
The CTO timer uses the UART bit times for its counter.
Note that STO and ETO timers use the pixel clock while
When spread spectrum is not enabled in MAX9257A:
When spread spectrum is enabled in MAX9257A:
max(T3)
max(T5)
t
max(T3)
max(T5)
T
max(T1) = 2.5Fs + (1400 x t
= pixel clock period, t
max(T1) = 2.5Fs + (3 x t
=
=
=
=


















t
t






���������������������������������������������������������������� Maxim Integrated Products 33
STO
ETO
t
t
8
8
ETO
STO
Fully Programmable Serializer/Deserializer
8
8






T2 = t
T4 = t
+
+






STO/ETO Timer Programming
+
+
1090
1090
546
546
STO
ETO
UCLK












×
×
×
×
T
t
t
t
) + (4 x t
t
T
T
T
T
T
) + (4 x t
= UART period
+
+
+
+
(Table
(20 t
(20 t
(20 t
(20 t
×
×
×
×
UCLK
UCLK
UCLK
UCLK
UCLK
UCLK
26). Bypass
CTO Timer
with UART/I
)
(Figures
)
)
)
)
)
Table 26. CTO Counter Timeout Period
CTO uses the UART bit times. The UART period t
synchronizes with the UART bit times, which synchronize
every time the SYNC frame is sent.
When the CTO timer times out, INTEN bit in both devices
is set to 0 and the devices revert back to base mode.
If communication with the MAX9257A/MAX9258A is not
needed after initial program ming is complete, CTO may
be set to 000 (never come back). In this case, CTO never
expires and the devices stay in bypass mode until they
are powered down. This prevents accidental program-
ming of the devices while ECU communicates with the
peripheral using a different UART protocol from the
MAX9257A/MAX9258A UART protocol.
The overall CTO timeout is calculated as follows:
Assuming a UART bit rate of 2Mbps, REG2[7:4],
REG3[7:4] = 100 (Table 26), CTO = 64, CTO timeout
calculated as:
The MAX9258A powers up when the power-down input
PD goes high. After approximately 130Fs, CCEN goes
high, indicating the control channel is available. This delay
is required because the analog circuitry has to fully wake
up. There are two ways to power up the MAX9257A. The
MAX9257A powers up according to the state of REM. ECU
powers up MAX9257A remotely (ECU sends command to
power up) when REM is pulled to V
powers up according to the supply voltage when REM is
grounded.
MAX9257A REG2[7:4]
MAX9258A REG3[7:4]
MAX9257A/MAX9258A
2
000
001
010
011
100
101
110
111
C Control Channel
t
CTO
t
CTO
= (0.5Fs) O 64 = 32Fs
= t
UCLK
COUNTER USING UART BIT
x CTO
Never come back
CC
Link Power-Up
(lockout)
TIMES
. The MAX9257A
112
16
32
48
64
80
96
UCLK