24LC00-/OT MICROCHIP [Microchip Technology], 24LC00-/OT Datasheet - Page 15

• Manufacturer Part Number: 24LC00-/OT
• Manufacturer: MICROCHIP [Microchip Technology]

9.0
The External Device Select (EDS) pin is an open drain,
low active output and may be used by the system
designer for functions such as enabling other circuitry
when the 24LCS61/62 is being accessed. Because the
pin is an open drain output, a pull-up resistor is required
for proper operation of this pin. When the device is
powered up, the EDS pin will always be in the high-
impedance state (off). The EDS pin function is
controlled by using the output enable (OE) bit in the
control byte of each command. If the OE bit is high, the
EDS pin is enabled and if the OE bit is low the pin is
disabled. For the Assign Address command and
FIGURE 9-1:
 2004 Microchip Technology Inc.
EXTERNAL DEVICE SELECT
(EDS) PIN AND OUTPUT
ENABLE (OE) BIT
SCL
SDA
EDS
EDS
SCL
SDA
Start
Start
Bit
Bit
0
1
1
0
EDS PIN OPERATION
For commands such as the Assign Address command or standard read and
writes, the EDS pin will be asserted on this rising clock edge if the OE bit was set
to a one in the control byte. If the OE bit is a zero and the previous command
asserted it, then the EDS pin will be released by the device on this clock edge.
2
1
2
1
For commands such as the Clear Address command, the command is ter-
minated at this point with a Stop bit. The EDS pin will be asserted on this
rising clock edge if the OE bit was set to a one in the control byte. If the OE
bit is a zero and the previous command asserted it, then the EDS pin will be
released by the device at this point.
1
3
3
1
Control
Control
4
0
4
0
Byte
Byte
5
5
6
6
7
7
8
8
ACK
ACK
BIT
BIT
9
9
1
1
2
2
standard Read or Write commands, the EDS pin will
pull low (providing that the OE bit is set high) on the ris-
ing clock edge after the ack bit following the ID byte.
See Figure 9-1. For commands such as the Clear
Address command, the EDS pin will change states at
the rising clock edge just before the Stop bit. It is also
possible to control the EDS pin by sending a partial
command such as the control byte and ID byte for a
Write command followed by the Stop bit. The EDS pin
would change states just before the Stop bit as shown
in the lower portion of Figure 9-1. When the EDS pin
has changed states, it is latched and will remain in a
given state until another command is sent to the device
with the OE bit set to change the state of the pin, or
power to the device is removed.
3
3
ID Byte
ID Byte
4
4
24LCS61/24LCS62
5
5
6
6
7
7
8
8
ACK
ACK
BIT
BIT
9
9
1
Stop
BIT
2
3
DS21226E-page 15