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M14C64, M14C32

typical time is shorter. To make use of this, an ACK

polling sequence can be used by the master.

The sequence, as shown in Figure 8, is as follows:

– Initial condition: a Write is in progress.

– Step 1: the master issues a START condition

followed by a device select byte (first byte of the

new instruction).

– Step 2: if the memory is busy with the internal

write cycle, no ACK will be returned and the

master goes back to Step 1. If the memory has

terminated the internal write cycle, it responds

with an ACK, indicating that the memory is

ready to receive the second part of the next in-

struction (the first byte of this instruction having

been sent during Step 1).

Read Operations

Read operations are independent of the state of

the WC pin. On delivery, the memory content is set

at all “1’s” (FFh).

ed. The transfer is terminated by the master

generating a STOP condition. Care must be taken

to avoid address counter ’roll-over’ which could re-

sult in data being overwritten. Note that, for any

byte or page write mode, the generation by the

master of the STOP condition starts the internal

memory program cycle. This STOP condition trig-

gers an internal memory program cycle only if the

STOP condition is internally decoded immediately

after the ACK bit; any STOP condition decoded

ternal programming cycle. All inputs are disabled

until the completion of this cycle and the Memory

will not respond to any request.

Minimizing System Delays by Polling On ACK

During the internal write cycle, the memory discon-

nects itself from the bus, and copies the data from

its internal latches to the memory cells. The maxi-

Figure 8. Write Cycle Polling Flowchart using ACK

WRITE Cycle

in Progress

AI02165

Next

Operation is

Addressing the

Memory

START Condition

DEVICE SELECT

with RW = 0

ACK

Returned

YES

NO

YES

NO

ReSTART

STOP

Proceed

WRITE Operation

Proceed

Random Address

READ Operation

Send

Byte Address

First byte of instruction

with RW = 0 already

decoded by M14xxx