Host sends its acknowledgment of valid data via HostAck going high. Host sends it's acknowledgment of the byte by de-asserting HostAck low. ECP Reverse Command Cycle Figure 4. Enhanced Capabilities Port Reverse Command 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. Command cycle is then selected by Peripheral via PeriphAck going low. 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.