Rainbow-electronics MAX9258 Bedienungsanleitung PDF herunterladen (Seite 28)

MAX9257/MAX9258

The four bits of REG2[7:4] select the divide ratio (STODIV)

for the STO clock as a function of the pixel clock (Table

24). The timeout period is determined by counter bits

REG2[3:0] that increment once every STO clock period.

Write to REG2[3:0] to determine the counter end time.

The STO counter counts to the programmed STOCNT +

1. The ECU must begin communicating before STO times

out, otherwise, the control channel closes (Figure 22). The

STO timeout period is given by:

For example:

If the pixel clock frequency is set to 16MHz, STODIV is

set to 1010 (STODIV = 1024), and STOCNT is set to

1001 (STOCNT = 9), the STO timer counts with

15.625kHz STO clock (16MHz/1024) internally until it

reaches 10 and timer expires. The t

STO

is equal to t

1024 x 10 = 640µs.

The default value for STODIV is 1024 while the default

value for STOCNT is 0. That means the STO timeout

period is equal 1024 pixel clock cycles. Activity from

the ECU on the control channel shuts off the STO timer

and starts the ETO timer.

ETO Timer

The ETO (end timeout) timer closes the control channel

if the ECU stops communicating for the ETO timeout

period. Configure register REG3[7:4] for both the

MAX9257 and the MAX9258 to select the divide ratio

(ETODIV) for the ETO clock as a function of the pixel

clock (Table 25). The timeout period is determined by

STODIV STOCNT

STO

CLK

⎛

⎝

⎜

⎞

⎠

⎟

×× +

1()

28 ______________________________________________________________________________________

Fully Programmable Serializer/Deserializer

with UART/I

C Control Channel

REG3[7:4] ETODIV

00XX 16

0100 16

0101 32

0110 64

0111 128

1000 256

1001 512

1010 1024

1011 2048

1100 4096

1101 8192

1110 16,384

1111 32,768

Table 25. ETO Clock Divide Ratio

VIDEO

HSK

VSYNC_IN

SDI/O±

CCEN

DOUT_

FROZEN

T1 = TIME TO ENTER CONTROL CHANNEL

T2 = STO TIMEOUT PERIOD

T3 = CONTROL CHANNEL EXIT TIME DUE TO STO

HSK = HANDSHAKING BETWEEN THE MAX9257 AND THE MAX9258

Figure 22. Control Channel Closing Due to STO Timeout

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 53 54

MAX9257/MAX9258 1
C Control Channel 1

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