Canon BJC 6000 Service Manual - Page 84
ECP mode, Interface Timing ECP mode, reverse transfer
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Part 4: Technical Reference BJC-6000 2.1.3 ECP mode The ECP mode allows data to be transferred bi-directionally between the printer and host computer. This mode also allows 2 byte data transfer to provide faster data transmission and reception. It is for this reason that ECP mode is suitable for transferring large amounts of data. In response to the fall of the ReverseRequest signal, the direction of the data bus switches from forward data transfer mode to reverse data transfer mode. The forward data transfer mode allows data to be transferred from the host computer to the printer, whereas the reverse data transfer mode allows data to be transferred from the printer to the host computer. (1) The host computer causes AckReverse to go low to request reverse data transfer (data transfer from printer to host computer). (2) After confirming AckReverse is low, the printer causes AckReverse to go low to indicate that that reverse transfer is possible. (3) The printer sends 1 byte of data out on the data lines and causes PeriphAck to go high to tell that this data is not command but data. The printer then causes PeriphClk to go low to tell that this data is valid. (4) After confirming the signal in (3) is received, the host computer causes HostAck to go high. (5) The printer causes AckReverse to go high to have the data recorded in the host computer. (6) The host computer causes HostAck to go high to get ready for the next one byte of data. (7) The printer repeats the process above to send the next one byte of data. PeriphClk Host Ack Data (1~8) PeriphAck ReverseRequest AckReverse Byte0 Data Byte1 Cmd Reverse transfer phase Figure 4-11 Interface Timing (ECP mode, reverse transfer) 4-12