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Providing a Frame Sync
(Camera Applications)
The GPI/GPO provide a simple solution for camera appli
-
cations that require a Frame Sync signal from the ECU
(e.g. surround view systems). Connect the ECU Frame
Sync signal to the GPI input, and connect GPO output
to the camera Frame Sync input. GPI/GPO has a typical
delay of 275
µs. Skew between multiple GPI/GPO chan
-
nels is typically 115µs. If a lower skew signal is required,
connect the camera’s frame sync input one of the deseri
-
alizer’s GPIOs and use an I
2
C broadcast write command
to change the GPIO output state. This has a maximum
skew of 0.5
µ
s + 1 I
2
C bit time.
Software Programming of the
Device Addresses
The serializers and deserializers have programmable
device addresses. This allows multiple GMSL devices,
along with I
2
C peripherals, to coexist on the same control
channel. The serializer device address is in register 0x00
of each device, while the deserializer device address is in
register 0x01 of each device. To change a device address,
first write to the device whose address changes (register
0x00 of the serializer for serializer device address change,
or register 0x01 of the deserializer for deserializer device
address change). Then write the same address into the
corresponding register on the other device (register 0x00
of the deserializer for serializer device address change,
or register 0x01 of the serializer for deserializer device
address change).
3-Level Configuration Inputs
CONF[1:0], ADD[1:0] and BWS are 3-level inputs that
control the serial interface configuration and power-up
defaults. Connect 3-level inputs through a pullup resistor
to IOVDD to set a high level, a pulldown resistor to GND
to set a low level, or open to set a mid level. For digital
control, use three-state logic to drive the 3-level logic
input.
Configuration Blocking
The serializers can block changes to registers. Set
CFGBLOCK to make registers 0x00 to registers 0x1F as
read only. Once set, the registers remain blocked until the
supplies are removed or until
PWDN
is low.
Compatibility with other GMSL Devices
The serializers are designed to pair with the MAX9276–
MAX9282 deserializers but interoperates with any GMSL
deserializers. See the
for operating limitations.
Key Memory
Each device has a unique HDCP key set that is stored
in secure nonvolatile memory (NVM). The HDCP key set
consists of forty 56-bit private keys and one 40-bit public
key. The NVM is qualified for automotive applications.
Table 19. MAX9277/MAX9281 Feature Compatibility
MAX9277/MAX9281 FEATURE
GMSL DESERIALIZER
HDCP (MAX9281 only)
If feature not supported in deserializer, must not be turned on in the MAX9281.
High-bandwidth mode
If feature not supported in deserializer, must only use 24-bit and 32-bit modes.
I
2
C to I
2
C
If feature not supported in deserializer, must use UART to I
2
C or UART to UART.
Coax
If feature not supported in deserializer, must connect unused serial input through 200nF and
50Ω in series to V
DD
and set the reverse control channel amplitude to 100mV.
High-immunity control channel
If feature not supported in deserializer, must use the legacy reverse control channel mode
TDM encoding
If feature not supported in deserializer, must use I
2
S encoding (with 50% WS duty cycle),
if supported.
I
2
S encoding
If feature not supported in deserializer must disable I
2
S in the MAX9277/MAX9281.
MAX9277/MAX9281
3.12Gbps GMSL Serializers for Coax or
STP Output Drive and LVDS Input
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