C control channel – Rainbow Electronics MAX9258 User Manual

Page 19

parity encoding that adds two parity bits to the serial
word. Bit 0 (EN0) is the LSB that is serialized first with-
out parity enabled. The parity bits are serialized first
when parity is enabled.

The ECU programs the MAX9258, MAX9257, and
peripheral devices at startup and during the control
channel phase. In a digital video system, the control
channel phase occurs during the vertical blanking time
and synchronizes to the VSYNC signal. The programma-
ble active edge of VSYNC initiates the control channel
phase. Nonactive edge of VSYNC can transition at any
time after 8 x t

if MAX9257 spread is not enabled and

0.5/f

SSM

when enabled. At the end of video phase, the

MAX9258 drives CCEN high to indicate to the ECU that

the control channel is open. Programmable timers and
ECU signal activity determine how long the control
channel stays open. The timers are reset by ECU signal
activity. ECU programming must not exceed the vertical
blanking time to avoid loss of video data.

After the control channel phase closes, the MAX9257
sends a 546 or 1090 word pattern as handshaking
(HSK) to synchronize the MAX9258’s internal clock
recovery circuit to the MAX9257’s transmitted data.
Following the handshaking, the control channel is
closed and the video phase begins. The serial LVDS
data is recovered and parallel data is valid on the pro-
grammed edge of the recovered pixel clock.

MAX9257/MAX9258

______________________________________________________________________________________

Fully Programmable Serializer/Deserializer

with UART/I

C Control Channel

VIDEO

HSK

CONTROL

VSYNC_IN

SDI/O

CCEN

HSK = HANDSHAKING

0.5/f

SSM

(max)

SPREAD

PROFILE

Figure 20. Video and Control Channel Phases (MAX9257 Spread is Enabled)