Host de-asserts HostClk high. Peripheral sends it's acknowledgment of the byte via de-asserting PeriphAck. ECP Reverse Data Cycle Figure 3. Enhanced Capabilities Port Reverse Data Cycle. Host sets nReverseRequest Low to request a reverse channel.
Peripheral acknowledges reverse channel request via asserting nAckReverse low.
Data is placed on data lines by Peripheral. Data cycle is then selected by Peripheral via PeriphAck going high. Valid data is indicated by the Peripheral setting PeriphClk low. Host sends its acknowledgment of valid data via HostAck going high. Host sends it's acknowledgment of the byte by de-asserting HostAck low.