Datasheet

3−10
transfers, which is the maximum specified frequency for standard-mode I
2
C. The serial EEPROM must be located
at address A0h. Figure 3−8 illustrates an example application implementing the two-wire serial bus.
Serial
EEPROM
PCI1510
MFUNC4
MFUNC1
SCL
SDA
V
CC
VCCD0
VCCD1
A2
A1
A0
5 V
Figure 3−8. Serial EEPROM Application
Some serial device applications may include PC Card power switches, ZV source switches, card ejectors, or other
devices that may enhance the user’s PC Card experience. The serial EEPROM device and PC Card power switches
are discussed in the sections that follow.
3.6.2 Serial-Bus Interface Protocol
The SCL and SDA signals are bidirectional, open-drain signals and require pullup resistors as shown in Figure 3−8.
The controller, which supports up to 100-Kb/s data-transfer rate, is compatible with standard mode I
2
C using 7-bit
addressing.
All data transfers are initiated by the serial bus master. The beginning of a data transfer is indicated by a start
condition, which is signaled when the SDA line transitions to low state while SCL is in the high state, as illustrated
in Figure 3−9. The end of a requested data transfer is indicated by a stop condition, which is signaled by a low-to-high
transition of SDA while SCL is in the high state, as shown in Figure 3−9. Data on SDA must remain stable during the
high state of the SCL signal, as changes on the SDA signal during the high state of SCL are interpreted as control
signals, that is, a start or a stop condition.
SDA
SCL
Start
Condition
Stop
Condition
Change of
Data Allowed
Data Line Stable,
Data Valid
Figure 3−9. Serial-Bus Start/Stop Conditions and Bit Transfers
Data is transferred serially in 8-bit bytes. The number of bytes that may be transmitted during a data transfer is
unlimited; however, each byte must be completed with an acknowledge bit. An acknowledge (ACK) is indicated by
the receiver pulling the SDA signal low, so that it remains low during the high state of the SCL signal. Figure 3−10
illustrates the acknowledge protocol.