MB8508S064CE-100 Datasheet, PDF (15/20 Pages) Fujitsu Component Limited. – 8 M x 64 BIT SYNCHRONOUS DYNAMIC RAM SO-DIMM

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MB8508S064CE-100/-100L
ACKNOWLEDGE
Acknowledge is a software convention used to indicate successful data transfer. The transmitting device, either
master or slave, will release the bus after transmitting eight bits. During the ninth clock cycle the receiver will
put the SDA line to Low in order to acknowledge that it received the eight bits of data.
The SPD will respond with an acknowledge when it received the start condition followed by slave address issued
by master.
In the read operation, the SPD will transmit eight bits of data, release the SDA line and monitor the line for an
acknowledge. If an acknowledge is detected and no stop condition is issued by master, the SPD will continue
to transmit data. If an acknowledge is not detected, the SPD will terminated further data transmissions. The
master must then issue a stop condition to return the SPD to the standby power mode.
In the write operation, upon receipt of eight bits of data the SPD will respond with an acknowledge, and await
the next eight bits of data, again responding with an acknowledge until the stop condition is issued by master.
SLAVE ADDRESS ADDRESSING
Following a start condition, the master must output the eight bits slave address. The most significant four bits
of the slave address are device type identifier. For the SPD this is fixed as 1010[B]. Refer to the Fig. 2 below.
The next three significant bits are used to select a particular device. A system could have up to eight SPD
devices —namely up to eight modules— on the bus. The eight addresses for eight SPD devices are defined
by the state of the SA0, SA1 and SA2 inputs. For this module, the three bits are fixed as 000[B] because all
addresses are driven to VSS on the module. Therefore, no address inputs are required.
The last bit of the slave address defines the operation to be performed. When R/W bit is “1”, a read operation
is selected, when R/W bit is “0”, a write operation is selected.
Following the start condition, the SPD monitors the SDA line comparing the slave address being transmitted
with its slave address (device type and state of SA0, SA1, and SA2 inputs). Upon a correct compare the SPD
outputs an acknowledge on the SDA line. Depending on the state of the R/W bit, the SPD will execute a read
or write operation.
Fig. 2 – SLAVE ADDRESS
DEVICE TYPE
IDENTIFIER
DEVICE
ADDRESS
1
0
1
0
SA2 SA1 SA0 R/W
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