SB4002A_Data Sheet_EN

SB4002A

that it cannot execute the transaction, it asserts STOP# instead of TRDY# at CLK 3. The master

checks STOP# at CLK 4, and deasserts FRAME#. At CLK 5, the master deasserts IRDY#, and the

target deasserts STOP# and DEVSEL#, terminating the transaction with RETRY,

Disconnect

The target terminates transaction when it cannot continue the burst from the master after it

transfers at least one data signal. If the master outputs the request for burst access to the target

that cannot continue the burst access, the target may complete the first data phase and terminates

the transaction with Disconnect.

Disconnect is divided into with data and without data. For with data, the target terminates

transaction after transfering the data at the last data phase, and for without data, the target

terminates transaction without transfering the data at the last data phase. For with data, both

TRDY# and STOP# are asserted at the same time at the last data phase, and for without data, the

target deasserts TRDY# and asserts STOP#, terminating the transaction with Disconnect.

IRDY#

4 6

TRDY#

FRAME#

CLK

DEVSEL#

STOP#

Figure 2-5. Disconnect With Data

In the above figure, a transaction is started normally at CLK 1 or CLK 2. If the burst access is

unavailable at CLK 3, the target asserts STOP#3, indicating that it will disconnect. At CLK 4, the

master checks STOP#, deasserts FRAME#, and then, terminates the transaction at CLK 5. In this

transaction, a data transfer occurs at CLK 3 (disconnect transaction), and at CLK 4 in which

STOP# is asserted (with data). If TRDY# is asserted at CLK 5, a data transfer occurs.