X24001
Read Operation
The byte read operation is initiated with a start condition.
The start condition is followed by an eight-bit control byte
which consists of a two-bit read command (1,0), four
address bits, and two “don’t care” bits. After receipt of
the control byte, the X24001 will enter the read mode
and transfer data into the shift register from the array.
This data is shifted out of the device on the next eight
SCL clocks. At the end of the read, all counters are reset
and the X24001 will enter the standby mode. As with a
write, the read operation can be interrupted by a start or
stop condition while the command or address is being
clocked in. While clocking data out, starts or stops
cannot be generated.
During the second don’t care clock cycle, starts and
stops are ignored. The master must free the bus prior to
the end of this clock cycle to allow the X24001 to begin
outputting data (Figures 4 and 5).
Figure 4. Read Sequence
START
1
0
A3 A2 A1 A0 XX XX D7 D6 D5 D4 D3 D2 D1 D0
3830 FHD F06
Figure 5. Read Cycle Timing
SCK
6
7
8
1
SDA IN
A0
XX
XX
SDA OUT
D7
D6
3830 FHD F07
SYMBOL TABLE
WAVEFORM
INPUTS
Must be
steady
May change
from LOW
to HIGH
May change
from HIGH
to LOW
Don’t Care:
Changes
Allowed
N/A
OUTPUTS
Will be
steady
Will change
from LOW
to HIGH
Will change
from HIGH
to LOW
Changing:
State Not
Known
Center Line
is High
Impedance
5
XICOR [ XICOR INC. ]
