X76F641 データシートの表示（PDF） - IC MICROSYSTEMS

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コンポーネント説明

メーカー

X76F641

Secure Serial Flash

IC MICROSYSTEMS 

X76F641

Figure 5. Acknowledge Polling

SCL

8th clk.

of 8th

pwd. byte

‘ACK’

clk

8th

‘ACK’

clk

clk

SDA

‘ACK’

START

condition

8th bit

ACK or

no ACK

7025 FM 10

READ OPERATIONS

Sequential Read

Read operations are initiated in the same manner as write The host can read sequentially within an array after the

operations but with a different command code.

password acceptance sequence. The data output is

sequential, with the data from address n followed by the data

Random Read

from n+1. The address counter for read operations

The master issues the start condition and a Read instruc- increments all address bits, allowing the entire memory

tion and password, performs a Password Ack Polling, then array contents to be serially read during one operation. At

issues the word address. Once the password has been the end of the address space (address 1FFFh for array 0,

acknowledged and first byte has been read, another start 1Fh for array 1), the counter “rolls over” to address 0 and the

can be issued followed by a new 8-bit address. Random X76F641 continues to output data for each acknowl- edge

reads are allowed, but only the low order 8 bits can received. Refer to figure 7 for the address, acknowledge

change. This limits random reads to a 256 byte block. edge and data transfer sequence. An acknowledge must

Therefore, with a single password cycle only a 256 byte follow each 8-bit data transfer. After the last bit has been

block of array 0 may be accessed randomly. To randomly read, a stop condition is generated without a preceding

access another block of array 0, a stop must be issued fol- acknowledge.

lowed by a new command/address/password sequence.

A random read of the array 1 can access all locations with-

out another password command sequence.

Figure 6. Random Read

SDA S

COMMAND

Read

Password

7

Read

Password

0

Wait tWC

OR

Repeated

ACK Polling

Command

If ACK, then

Password Matches

ACK POLLING

COMMAND

S

S

Data X

S

Data Y

7025 FM 11

7

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