Rainbow-electronics MAX7470 Bedienungsanleitung PDF herunterladen (Seite 10)

MAX7469/MAX7470

HDTV Continuously Variable

Anti-Aliasing Filters

10 _______________________________________________________________________________________

START and STOP Conditions

A master device initiates communication by issuing a

START condition, a high-to-low transition on SDA with SCL

high (Figure 2). The master terminates transmission by a

STOP condition (see the

Acknowledge Bit (ACK) and Not-

Acknowledge Bit (NACK)

section). A STOP condition is a

low-to-high transition on SDA while SCL is high (Figure 2).

The STOP condition frees the bus. If a repeated START

condition is generated instead of a STOP condition, the

bus remains active. When a STOP condition or incorrect

address is detected, the MAX7469/

MAX7470 then ignore all communication on the I

C bus

until the next START or REPEATED START condition,

minimizing digital noise and feedthrough.

Early STOP Conditions

The MAX7469/MAX7470 recognize a STOP condition at

any point during transmission except when a STOP

condition occurs in the same high pulse as a START

condition (Figure 3). This condition is not a legal I

C for-

mat; at least one clock pulse must separate any START

and STOP conditions. The MAX7469/MAX7470 discard

any data received during a data transfer aborted by an

early STOP condition.

Repeated START (S

) Conditions

An Sr condition is used to indicate a change in direc-

tion of data flow (see the

Read Cycle

section). Sr can

also be used when the bus master is writing to several

C devices and does not want to relinquish control of

the bus. The MAX7469/MAX7470 serial interface sup-

ports continuous write operations with (or without) an Sr

condition separating them.

START

STARTSTOP

ILLEGAL STOP

LEGAL STOP CONDITION ILLEGAL STOP CONDITION

SCL

SDA

SCL

SDA

Figure 3. Early STOP Conditions

SCL

SDA

Figure 2. START/STOP Conditions

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 16 17

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