MAX7300 Maxim, MAX7300 Datasheet - Page 9

• Manufacturer Part Number: MAX7300
• Description: The MAX7300 compact, serial-interfaced, I/O expansion peripheral provides microprocessors with up to 28 ports
• Manufacturer: Maxim

Any bytes received after the command byte are consid-
ered data bytes. The first data byte goes into the inter-
nal register of the MAX7300 selected by the command
byte (Figure 8). If multiple data bytes are transmitted
before a STOP condition is detected, these bytes are
generally stored in subsequent MAX7300 internal regis-
ters because the command byte address generally
autoincrements (Table 4).
The MAX7300 is read using the MAX7300’s internally
stored command byte as address pointer, the same way
the stored command byte is used as address pointer for
Figure 2. 2-Wire Serial Interface Timing Details
Figure 3. Start and Stop Conditions
Figure 4. Bit Transfer
SDA
SCL
t
HD, STA
START CONDITION
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
_______________________________________________________________________________________
Message Format for Reading
SDA
SCL
t
LOW
CONDITION
t
SDA
SCL
R
START
S
t
HIGH
t
SU, DAT
t
F
DATA LINE STABLE; DATA VALID CHANGE OF DATA ALLOWED
t
HD, DAT
t
SU, STA
REPEATED START CONDITION
a write. The pointer generally autoincrements after each
data byte is read using the same rules as for a write
(Table 4). Thus, a read is initiated by first configuring the
MAX7300’s command byte by performing a write (Figure
7). The master can now read ‘n’ consecutive bytes from
the MAX7300, with the first data byte being read from the
register addressed by the initialized command byte
(Figure 9). When performing read-after-write verification,
remember to reset the command byte’s address
because the stored control byte address generally has
been autoincremented after the write (Table 4). Table 5
is the register address map.
28-Port I/O Expander
t
HD, STA
CONDITION
STOP
P
t
SU, STO
STOP CONDITION
t
BUF
START CONDITION
9