adv7322 Analog Devices, Inc., adv7322 Datasheet - Page 24

• Manufacturer Part Number: adv7322
• Description: Multiformat 11-bit Hdtv Video Encoder
• Manufacturer: Analog Devices, Inc.

ADV7322
MPU PORT DESCRIPTION
The ADV7322 supports a 2-wire serial (I
microprocessor bus driving multiple peripherals. This port
operates in an open-drain configuration. Two inputs, serial data
(SDA) and serial clock (SCL), carry information between any
device connected to the bus and the ADV7322. Each slave
device is recognized by a unique address. The ADV7322 has
four possible slave addresses for both read and write operations.
These are unique addresses for each device and are illustrated in
Figure 44. The LSB sets either a read or write operation. Logic 1
corresponds to a read operation, while Logic 0 corresponds to a
write operation. A1 is set by setting the ALSB pin of the
ADV7322 to Logic 0 or Logic 1. When ALSB is set to 1, there is
greater input bandwidth on the I
speed data transfers on this bus. When ALSB is set to 0, there is
reduced input bandwidth on the I
pulses of less than 50 ns will not pass into the I
controller. This mode is recommended for noisy systems.
To control the various devices on the bus, the following protocol
must be followed. First the master initiates a data transfer by
establishing a start condition, defined by a high-to-low
transition on SDA while SCL remains high. This indicates that
an address/data stream will follow. All peripherals respond to
the start condition and shift the next eight bits (7-bit address +
R/ W bit). The bits are transferred from MSB down to LSB. The
peripheral that recognizes the transmitted address responds by
pulling the data line low during the ninth clock pulse. This is
known as an acknowledge bit. All other devices withdraw from
the bus at this point and maintain an idle condition. The idle
condition is where the device monitors the SDA and SCL lines
waiting for the start condition and the correct transmitted
address. The R/ W bit determines the direction of the data.
Logic 0 on the LSB of the first byte means that the master will
write information to the peripheral. Logic 1 on the LSB of the
first byte means that the master will read information from the
peripheral.
1
Figure 44. ADV7322 Slave Address = 0xD4
1
0
1
0
2
C lines, which allows high
2
C lines, which means that
1
SET UP BY
ADDRESS
CONTROL
ALSB
2
A1
C-compatible)
READ/WRITE
CONTROL
0
1
2
WRITE
READ
X
C internal
Rev. PrA | Page 24 of 88
The ADV7322 acts as a standard slave device on the bus. The
data on the SDA pin is eight bits long, supporting the 7-bit
addresses plus the R/ W bit. It interprets the first byte as the
device address and the second byte as the starting subaddress.
There is a subaddress auto-increment facility. This allows data
to be written to or read from registers in ascending subaddress
sequence starting at any valid subaddress. A data transfer is
always terminated by a stop condition. The user can also access
any unique subaddress register on a one-by-one basis without
having to update all the registers.
Stop and start conditions can be detected at any stage during
the data transfer. If these conditions are asserted out of
sequence with normal read and write operations, then they
cause an immediate jump to the idle condition. During a given
SCL high period, the user should only issue one start condition,
one stop condition, or a single stop condition followed by a
single start condition. If an invalid subaddress is issued by the
user, the ADV7322 will not issue an acknowledge and will
return to the idle condition. If in auto-increment mode the user
exceeds the highest subaddress, the following action is taken:
1.
2.
Before writing to the subcarrier frequency registers, it is a
requirement that the ADV7322 is reset at least once after
power-up.
The four subcarrier frequency registers must be updated,
starting with subcarrier frequency register 0 through subcarrier
frequency register 3. The subcarrier frequency will not update
until the last subcarrier frequency register byte has been
received by the ADV7322.
Figure 45 illustrates an example of data transfer for a write
sequence and the start and stop conditions. Figure 46 shows bus
write and read sequences.
In read mode, the highest subaddress register contents are
output until the master device issues a no-acknowledge.
This indicates the end of a read. A no-acknowledge
condition is when the SDA line is not pulled low on the
ninth pulse.
In write mode, the data for the invalid byte is not loaded
into any subaddress register, a no-acknowledge is issued by
the ADV7322, and the part returns to the idle condition.
Preliminary Technical Data