LM1238AAD/NA National Semiconductor, LM1238AAD/NA Datasheet - Page 17

• Manufacturer Part Number: LM1238AAD/NA
• Manufacturer: National Semiconductor

Specifications of LM1238AAD/NA

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Package Type: MDIP
• Lead Free Status / RoHS Status: Not Compliant

Microcontroller Interface
The microcontroller interfaces to the LM1238 preamp via the
I
with a Start Pulse followed by a byte comprised of a seven
bit Slave Device Address and a Read/Write bit. Since the
first byte is composed of both the address and the read/write
bit, the address of the LM1238 for writing is 0xBA
(10111010b) and the address for reading is 0xBB
(10111011b). The development software provided by Na-
tional Semiconductor will automatically take care of the dif-
ference between the read and write addresses if the target
address under the communications tab is set to 0xBA. Fig-
ure 15 and Figure 16 show a write and read sequence on the
I
READ SEQUENCE
Read sequences are comprised of two I
fer sequences: The first is a write sequence that only trans-
fers the two byte address to be accessed. The second is a
read sequence that starts at the address transferred in the
previous address only write access and increments to the
next address upon every data byte read. This is shown in
Figure 16. The write sequence consists of the Start Pulse,
the Slave Device Address, the Read/Write bit (a zero, indi-
cating a write) and the Acknowledge bit; the next byte is the
least significant byte of the address to be accessed, followed
by its Acknowledge bit. This is then followed by a byte
2
2
C compatible interface. The protocol of the interface begins
C compatible interface.
2
FIGURE 15. I
C compatible trans-
2
C Compatible Write Sequence
17
WRITE SEQUENCE
The write sequence begins with a start condition which
consists of the master pulling SDA low while SCL is held
high. The slave device address is next sent. The address
byte is made up of an address of seven bits (7-1) and the
read/write bit (0). Bit 0 is low to indicate a write operation.
Each byte that is sent is followed by an acknowledge. When
SCL is high the master will release the SDA line. The slave
must pull SDA low to acknowledge. The register to be written
to is next sent in two bytes, the least significant byte being
sent first. The master can then send the data, which consists
of one or more bytes. Each data byte is followed by an
acknowledge bit. If more than one data byte is sent the data
will increment to the next address location. See Figure 15.
containing the most significant address byte, followed by its
Acknowledge bit. Then a Stop bit indicates the end of the
address only write access. Next the read data access will be
performed beginning with the Start Pulse, the Slave Device
Address, the Read/Write bit ( a one, indicating a read) and
the Acknowledge bit. The next 8 bits will be the read data
driven out by the LM1238 preamp associated with the ad-
dress indicated by the two address bytes. Subsequent read
data bytes will correspond to the next increment address
locations. Data should only be read from the LM1238 when
both OSD windows are disabled.
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