ISL12024 Datasheet, PDF (18/25 Pages) Intersil Corporation – Real-Time Clock/Calendar with Embedded Unique ID

ISL12024
S
SIGNALS FROM
THE MASTER
T
A
R
T
SLAVE
ADDRESS
WORD
ADDRESS 1
WORD
ADDRESS 0
1 ≤ n ≤ 16 for EEPROM ARRAY
1 ≤ n ≤ 8 for CCR
DATA
(1)
S
DATA
(n)
T
O
P
SDA BUS
1
1 1 10 000 00 0 0
A
A
A
A
SIGNALS FROM
C
C
C
C
THE SLAVE
K
K
K
K
FIGURE 18. PAGE WRITE SEQUENCE
Acknowledge Polling
Disabling of the inputs during non-volatile write cycles can
be used to take advantage of the 12ms (typ) write cycle time.
Once the stop condition is issued to indicate the end of the
master’s byte load operation, the ISL12024 initiates the
internal non-volatile write cycle. Acknowledge polling can
begin immediately. To do this, the master issues a start
condition followed by the Memory Array Slave Address Byte
for a write or read operation (AEh or AFh). If the ISL12024 is
still busy with the non-volatile write cycle, then no ACK will
be returned. When the ISL12024 has completed the write
operation, an ACK is returned and the host can proceed with
the read or write operation. See the flow chart in
Figure 20. Note: Do not use the CCR Slave byte (DEh or
DFh) for Acknowledge Polling.
Read Operations
There are three basic read operations: Current Address
Read, Random Read and Sequential Read.
Current Address Read
Internally the ISL12024 contains an address counter that
maintains the address of the last word read incremented by
one. Therefore, if the last read was to address n, the next
read operation would access data from address n+1. On
power-up, the 16-bit address is initialized to 00h. In this way,
a current address read immediately after the power-on reset
can download the entire contents of memory starting at the
first location. Upon receipt of the Slave Address Byte with
the R/W bit set to one, the ISL12024 issues an
acknowledge, then transmits 8 data bits. The master
terminates the read operation by not responding with an
acknowledge during the ninth clock and issuing a stop
condition. See Figure 19 for the address, acknowledge, and
data transfer sequence.
S
T
S
SIGNALS FROM
A
SLAVE
T
THE MASTER
R ADDRESS
O
T
P
SDA BUS
SIGNALS FROM
THE SLAVE
1
1 1 11
A
C
DATA
K
FIGURE 19. CURRENT ADDRESS READ SEQUENCE
BYTE LOAD
COMPLETED BY
ISSUING STOP.
ENTER ACK POLLING
ISSUE START
ISSUE MEMORY ARRAY SLAVE
ADDRESS BYTE
AFH (READ) OR AEH (WRITE)
ISSUE STOP
NO
ACK
RETURNED?
YES
NO
NON-VOLATILE WRITE
CYCLE COMPLETE. CONTINUE
COMMAND SEQUENCE?
YES
CONTINUE
NORMAL READ OR
WRITE COMMAND
SEQUENCE
ISSUE STOP
PROCEED
FIGURE 20. ACKNOWLEDGE POLLING SEQUENCE
18
FN6370.3
August 18, 2008