AT88SC0104CA_11 ATMEL [ATMEL Corporation], AT88SC0104CA_11 Datasheet - Page 32

• Manufacturer Part Number: AT88SC0104CA_11
• Description: Atmel CryptoMemory Specification Datasheet
• Manufacturer: ATMEL [ATMEL Corporation]

8.8
8.8.1
Random Read: $B1
Functional
Figure 8-7. Random Read Sequence Description
The Random Read command $B1 allows reading of data from the devices configuration memory or currently selected user
zone (The Section 8.10 System Write: $B4 describes how to select a user zone).
The random read command provides the host ability to sequentially clock data from the device starting from a specified
address. The host needs to first specify the start address to read from in the memory by executing a “dummy” operation. The
host does this by clocking in the four bytes of the write command and then follows them with a start condition instead of a data
byte. At this point, the device’s internal logic is pointing to the address from the aborted write operation. The host may then
issue the random read command byte ($B1) to which the device will respond with the EEPROM byte at the current address
location and then increment the internal address by one. The device will continue to sequentially send out bytes as long as the
host keeps acknowledging each byte with an ACK. During this operation the address will “roll over” from the last byte of the
current zone to the first byte of the same zone. The host terminates random read by issuing a NACK signal instead of an ACK.
Figure 8-8. Random Read Command Structure
S
T
A
R
T
Command
xxxx xxx0
WRITE
A
C
K
Host
Write Command
Address A1
Address A2
Number of bytes N
Random Read Command
0000 0000
Address 1
A
C
K
0a6-- ---a0
Address 2
Atmel AT88SC0104CA/0204CA/0404CA/0808CA [Datasheet]
A
C
K
Device
Data
…
Data
n7--- ---n0
N
A
C
K
N
A
C
K
S
T
A
R
T
Random Read
Command
xxxx 0001
N data bytes
A
C
K
d7--- ---d0
Data
8664E−CRYPTO−12/11
A
C
K
d7--- ---d0
Data x N
N
C
32
A
K
O
S
P
T