24C04A
9.0
READ MODE
Note 1: If the master knows where the address
pointer is, it can begin the read sequence
at the current address (Figure 9-1) and
save time transmitting the slave and word
addresses.
In this mode the 24C04A transmits data to the master
devide.
As can be seen from Figure 9-2 and Figure 9-3, the
master first sets up the slave and word addresses by
doing a write. (Note: Although this is a read mode, the
address pointer must be written to). During this period
the 24C04A generates the necessary acknowledge bits
as defined in the appropriate section.
Note 2: In all modes, the address pointer will not
increment through a block (256 byte)
boundary, but will rotate back to the first
location in that block.
The master now generates another START condition
and transmits the slave address again, except this time
the read/write bit is set into the read mode. After the
slave generates the acknowledge bit, it then outputs
the data from the addressed location on to the SDA pin,
increments the address pointer and, if it receives an
acknowledge from the master, will transmit the next
consecutive byte. This auto-increment sequence is
only aborted when the master sends a STOP condition
instead of an acknowledge.
FIGURE 9-1: CURRENT ADDRESS READ
S
T
A
R
T
S
BUS ACTIVITY
MASTER
CONTROL
BYTE
T
DATA n
O
P
SDA LINE
S
P
A
C
K
N
O
BUS ACTIVITY
A
C
K
FIGURE 9-2: RANDOM READ
S
T
A
R
T
S
T
A
R
T
S
T
O
P
BUS ACTIVITY
MASTER
CONTROL
BYTE
WORD
ADDRESS (n)
CONTROL
BYTE
DATA (n)
S
P
S
SDA LINE
A
C
K
A
C
K
A
C
K
N
O
BUS ACTIVITY
A
C
K
FIGURE 9-3: SEQUENTIAL READ
S
T
O
P
BUS ACTIVITY
MASTER
CONTROL
BYTE
DATA n
DATA n + 1
DATA n + 2
DATA n + X
SDA LINE
P
A
C
K
A
C
K
A
C
K
A
C
K
N
O
BUS ACTIVITY
A
C
K
DS11183F-page 8
2004 Microchip Technology Inc.
ROCHESTER [ Rochester Electronics ]
