24LCS22A
DS21682E-page 14 2009 Microchip Technology Inc.
8.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 8-1.
TABLE 8-1: PIN FUNCTION TABLE
8.1
Write-Protect
(WP)
This pin is used for flexible write protection of the
24LCS22A. When memory location 7Fh is written with
any data, this pin is enabled and determines the write
capability of the 24LCS22A (Table 6-1).
8.2 Serial Address/Data Input/Output
(SDA)
This pin is used to transfer addresses and data into and
out of the device, when the device is in the Bidirectional
mode. In the Transmit-Only mode, which only allows
data to be read from the device, data is also transferred
on the SDA pin. This pin is an open drain terminal,
therefore the SDA bus requires a pull-up resistor to
V
CC (typical 10 k for 100 kHz, 2 k for 400 kHz).
For normal data transfer in the Bidirectional mode, SDA
is allowed to change only during SCL low. Changes
during SCL high are reserved for indicating the Start
and Stop conditions.
8.3 Serial Clock (SCL)
This pin is the clock input for the Bidirectional mode,
and is used to synchronize data transfer to and from the
device. It is also used as the signaling input to switch
the device from the Transmit-Only mode to the
Bidirectional mode. It must remain high for the chip to
continue operation in the Transmit-Only mode.
8.4 Serial Clock (VCLK)
This pin is the clock input for the Transmit-Only mode
(DDC1). In the Transmit-Only mode, each bit is clocked
out on the rising edge of this signal. In the Bidirectional
mode, a high logic level is required on this pin to enable
write capability.
Name Function
WP
Write-Protect
(active low)
V
SS Ground
SDA Serial Address/Data I/O
SCL Serial Clock (Bidirectional mode)
VCLK Serial Clock (Transmit-Only mode)
V
CC +2.5V to 5.5V Power Supply
NC No Internal Connection
