ISL1219 Datasheet, PDF (19/24 Pages) Intersil Corporation – Low Power RTC with Battery Backed SRAM and Event Detection

ISL1219
Device Addressing
Following a start condition, the master must output a Slave
Address Byte. The 7 MSBs are the device identifier. These
bits are “1101111”. Slave bits “1101” access the register.
Slave bits “111” specify the device select bits.
The last bit of the Slave Address Byte defines a read or write
operation to be performed. When this R/W bit is a “1”, then a
read operation is selected. A “0” selects a write operation
(Refer to Figure 17).
After loading the entire Slave Address Byte from the SDA
bus, the ISL1219 compares the device identifier and device
select bits with “1101111”. Upon a correct compare, the
device outputs an acknowledge on the SDA line.
Following the Slave Byte is a one byte word address. The
word address is either supplied by the master device or
obtained from an internal counter. On power-up, the internal
address counter is set to address 0h, so a current address
read of the CCR array starts at address 0h. When required,
as part of a random read, the master must supply the 1 Word
Address Bytes as shown in Figure 18.
In a random read operation, the slave byte in the “dummy
write” portion must match the slave byte in the “read”
section. For a random read of the Clock/Control Registers,
the slave byte must be “1101111x” in both places.
1
1
0
1
11
1
R/W
SLAVE
ADDRESS BYTE
Write Operation
A Write operation requires a START condition, followed by a
valid Identification Byte, a valid Address Byte, a Data Byte,
and a STOP condition. After each of the three bytes, the
ISL1219 responds with an ACK. At this time, the I²C
interface enters a standby state.
Read Operation
A Read operation consists of a three byte instruction
followed by one or more Data Bytes (Figure 18). The master
initiates the operation issuing the following sequence: a
START, the Identification byte with the R/W bit set to “0”, an
Address Byte, a second START, and a second Identification
byte with the R/W bit set to “1”. After each of the three bytes,
the ISL1219 responds with an ACK. Then the ISL1219
transmits Data Bytes as long as the master responds with an
ACK during the SCL cycle following the eighth bit of each
byte. The master terminates the read operation (issuing a
STOP condition) following the last bit of the last Data Byte
(Figure 18).
The Data Bytes are from the memory location indicated by
an internal pointer. This pointer initial value is determined by
the Address Byte in the Read operation instruction, and
increments by one during transmission of each Data Byte.
After reaching the memory location 19h the pointer “rolls
over” to 00h, and the device continues to output data for
each ACK received.
A7 A6 A5 A4 A3 A2 A1 A0 WORD ADDRESS
D7 D6 D5 D4 D3 D2 D1 D0 DATA BYTE
FIGURE 17. SLAVE ADDRESS, WORD ADDRESS, AND DATA
BYTES
SIGNALS
FROM THE
MASTER
S
T _{IDENTIFICATION}
A
BYTE WITH
R
R/W=0
T
ADDRESS
BYTE
S
T _{IDENTIFICATION}
A _{BYTE WITH}
R
R/W = 1
T
S
A
A
T
C
C
O
K
K
P
SIGNAL AT
SDA
11011110
A
SIGNALS FROM
C
THE SLAVE
K
11011111
A
A
C
C _{FIRST READ}
K
K _{DATA BYTE}
LAST READ
DATA BYTE
FIGURE 18. READ SEQUENCE
19
FN6314.2
July 15, 2010