Cycle 1 - The bus is idle.
Cycle 2 - The initiator asserts a valid address and places a read command on the C/BE# signals. This is the address phase.
Cycle 3 - The initiator tri-states the address in preparation for the target driving read data. The initiator now drives valid byte enable information on the C/BE# signals. The initiator asserts IRDY# low indicating it is ready to capture read data. The target asserts DEVSEL# low (in this cycle or the next) as an acknowledgment it has positively decoded the address. The target drives TRDY# high indicating it is not yet providing valid read data.
Cycle 4 - The target provides valid data and asserts TRDY# low indicating to the initiator that data is valid. IRDY# and TRDY# are both low during this cycle causing a data transfer to take place. The initiator captures the data. This is the first data phase.
Cycle 5 - The target deasserts TRDY# high indicating it needs more time to prepare the next data transfer.
Cycle 6 - The second data phase occurs as both IRDY# and TRDY# are low. The initiator captures the data provided by the target.
Cycle 7 - The target provides valid data for the third data phase, but the initiator indicates it is not ready by deasserting IRDY# high.
Cycle 8 - The initiator re-asserts IRDY# low to complete the third data phase. The initiator captures the data provided by the target. The initiator drives FRAME# high indicating this is the final data phase (master termination).
Cycle 9 - FRAME#, AD, and C/BE# are tri-stated, as IRDY#, TRDY#, and DEVSEL# are driven inactive high for one cycle prior to being tri-stated.
Cycle 1 - The bus is idle.
Cycle 2 - The initiator asserts a valid address and places a read command on the C/BE# signals. This is the address phase.
Cycle 3 - The initiator tri-states the address in preparation for the target driving read data. The initiator now drives valid byte enable information on the C/BE# signals. The initiator asserts IRDY# low indicating it is ready to capture read data. The target asserts DEVSEL# low (in this cycle or the next) as an acknowledgment it has positively decoded the address. The target drives TRDY# high indicating it is not yet providing valid read data.
Cycle 4 - The target provides valid data and asserts TRDY# low indicating to the initiator that data is valid. IRDY# and TRDY# are both low during this cycle causing a data transfer to take place. The initiator captures the data. This is the first data phase.
Cycle 5 - The target deasserts TRDY# high indicating it needs more time to prepare the next data transfer.
Cycle 6 - The second data phase occurs as both IRDY# and TRDY# are low. The initiator captures the data provided by the target.
Cycle 7 - The target provides valid data for the third data phase, but the initiator indicates it is not ready by deasserting IRDY# high.
Cycle 8 - The initiator re-asserts IRDY# low to complete the third data phase. The initiator captures the data provided by the target. The initiator drives FRAME# high indicating this is the final data phase (master termination).
Cycle 9 - FRAME#, AD, and C/BE# are tri-stated, as IRDY#, TRDY#, and DEVSEL# are driven inactive high for one cycle prior to being tri-stated.
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