24AA256/24LC256

DS21203C-page 8

© 1998 Microchip Technology Inc.

7.0

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 no ACK

is returned, then the start bit and control byte must be

resent. 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 7-1 for

flow diagram.

FIGURE 7-1:

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

(ACK = 0)?

Next

Operation

NO

YES