24AA32_04 Datasheet, PDF (7/14 Pages) Microchip Technology – 32K 1.8V I2C™ Smart Serial™ EEPROM

5.0 ACKNOWLEDGE POLLING
Since the device will not acknowledge during a write
cycle, this can be used to determine when the cycle is
complete (this feature can be used to maximize bus
throughput). Once the stop condition for a write com-
mand has been issued from the master, the device ini-
tiates the internally timed write cycle. ACK polling can
be initiated immediately. This involves the master send-
ing a start condition followed by the control byte for a
write command (R/W = 0). If the device is still busy with
the write cycle, then no ACK will be returned. If the
cycle is complete, then the device will return the ACK
and the master can then proceed with the next read or
write command. See Figure 5-1 for flow diagram.
FIGURE 5-1: ACKNOWLEDGE POLLING
FLOW
Send
Write Command
Send Stop
Condition to
Initiate Write Cycle
Send Start
Send Control Byte
with R/W = 0
Did Device
Acknowledge
No
(ACK = 0)?
Yes
Next
Operation
24AA32
6.0 READ OPERATION
Read operations are initiated in the same way as write
operations with the exception that the R/W bit of the
slave address is set to one. There are three basic
types of read operations: current address read, random
read, and sequential read.
6.1 Current Address Read
The 24AA32 contains an address counter that main-
tains the address of the last word accessed, internally
incremented by one. Therefore, if the previous access
(either a read or write operation) was to address n (n is
any legal address), the next current address read oper-
ation would access data from address n + 1. Upon
receipt of the slave address with R/W bit set to one, the
24AA32 issues an acknowledge and transmits the
eight bit data word. The master will not acknowledge
the transfer but does generate a stop condition and the
24AA32 discontinues transmission (Figure 6-1).
6.2 Random Read
Random read operations allow the master to access
any memory location in a random manner. To perform
this type of read operation, first the word address must
be set. This is done by sending the word address to the
24AA32 as part of a write operation (R/W bit set to 0).
After the word address is sent, the master generates a
start condition following the acknowledge. This termi-
nates the write operation, but not before the internal
address pointer is set. Then the master issues the con-
trol byte again but with the R/W bit set to a one. The
24AA32 will then issue an acknowledge and transmit
the eight bit data word. The master will not acknowl-
edge the transfer but does generate a stop condition
which causes the 24AA32 to discontinue transmission
(Figure 6-2).
FIGURE 6-1: CURRENT ADDRESS READ
S
BUS ACTIVITY ^T
MASTER
A
R
T
CONTROL BYTE
SDA LINE
S
A
BUS ACTIVITY
C
K
DATA BYTE
S
T
O
P
P
N
O
A
C
K
 2004 Microchip Technology Inc.
DS21124E-page 7