24LC41IP datasheet(10/18 Pages) MICROCHIP

10 / 18 page

24LC41

DS21140F-page 10

 2004 Microchip Technology Inc.

5.0

ACKNOWLEDGE POLLING

Acknowledge polling can be done for both the DDC

Monitor Port (when in Bidirectional mode) and the

Microcontroller Access Port.

Since the port 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 but

throughput). Once the Stop condition for a Write

command has been issued from the master, the device

initiates the internally timed write cycle. ACK polling

can be initiated immediately. This involves the master

sending 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 the flow

diagram.

FIGURE 5-1:

ACKNOWLEDGE

POLLING FLOW

6.0

WRITE PROTECTION

6.1

DDC Monitor Port

When using the DDC Monitor Port in the Bidirectional

mode, the VCLK/DWP pin operates as the write-protect

control pin. Setting VCLK/DWP high allows normal

write

operations,

while

setting

VCLK/DWP

low

prevents writing to any location in the array. Connecting

the VCLK/DWP pin to VSS would allow the DDC Moni-

tor Port to operate as a serial ROM, although this

configuration would prevent using the device in the

Transmit-only mode.

6.2

Microcontroller Access Port

The Microcontroller Access Port can be used as a

serial ROM when the MWP pin is connected to VCC.

Programming will be inhibited and the entire memory

associated with the Microcontroller Access Port will be

write-protected.

Send

Write Command

Send Stop

Condition to

Initiate Write Cycle

Send Start

Send Control Byte

with R/W = 0

Did Device

Acknowledge

(ACK = 0)?

Operation

YES

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