Datasheet

MAX7314
Message Format for Reading
The MAX7314 is read using the MAX7314’s internally
stored command byte as an address pointer the same
way the stored command byte is used as an address
pointer for a write. The pointer autoincrements after
each data byte is read using the same rules as for a
write (Table 2). Thus, a read is initiated by first configur-
ing the MAX7314’s command byte by performing a
write (Figure 7). The master can now read n consecu-
tive bytes from the MAX7314 with the first data byte
being read from the register addressed by the initial-
ized command byte. When performing read-after-write
verification, remember to reset the command byte’s
address because the stored command byte address
has been autoincremented after the write (Table 2). A
diagram of a read from the input ports registers is
shown in Figure 10 reflecting the states of the ports.
Operation with Multiple Masters
If the MAX7314 is operated on a 2-wire interface with
multiple masters, a master reading the MAX7314 should
use a repeated start between the write, which sets the
MAX7314’s address pointer, and the read(s) that takes
the data from the location(s) (Table 2). This is because it
is possible for master 2 to take over the bus after master
1 has set up the MAX7314’s address pointer but before
master 1 has read the data. If master 2 subsequently
changes the MAX7314’s address pointer, then master
1’s delayed read can be from an unexpected location.
Command Address Autoincrementing
The command address stored in the MAX7314 circu-
lates around grouped register functions after each data
byte is written or read (Table 2).
18-Port GPIO with LED Intensity Control,
Interrupt, and Hot-Insertion Protection
10 ______________________________________________________________________________________
Figure 10. Read, Write, and Interrupt Timing Diagrams
SLAVE ADDRESS
123456789
SA6A5A4A3A2A1A00A0 000000
COMMAND BYTE
1A A AP
START CONDITION
ACKNOWLEDGE FROM SLAVE
ACKNOWLEDGE FROM SLAVE ACKNOWLEDGE FROM SLAVE STOP
CONDITION
P7–P0
P15– P8
DATA1 VALID
DATA2 VALID
SLAVE ADDRESS
123456789
S A6A5A4A3A2A1A0 1 A
COMMAND BYTE
ANA
START CONDITION
ACKNOWLEDGE FROM SLAVE
ACKNOWLEDGE FROM MASTER
P7–P0
P15–P8
STOP CONDITION
P
NO ACKNOWLEDGE FROM
MASTER
DATA2
DATA4DATA3
t
DV
t
DV
SLAVE ADDRESS
123456789
SA6A5A4A3A2A1A0 1 A
COMMAND BYTE
ANA
START CONDITION
ACKNOWLEDGE FROM SLAVE
ACKNOWLEDGE FROM MASTER
P7–P0
P15–P8
STOP CONDITION
P
NO ACKNOWLEDGE FROM
MASTER
DATA1 DATA2 DATA3 DATA4
DATA6DATA5
t
DH
t
DS
DATA1
t
IV
t
IR
t
IR
t
IV
SCL
SDA
SCL
SDA
SCL
SDA
WRITE TO OUTPUT PORTS REGISTERS (BLINK PHASE 0 REGISTERS/BLINK PHASE 1 REGISTERS)
READ FROM INPUT PORTS REGISTERS
INTERRUPT VALID/RESET
R/W
MSB LSBDATA1
MSB LSBDATA1
MSB LSBDATA2 MSB LSBDATA4
MSB LSBDATA6
MSB LSBDATA2
R/W
R/W
INT