Canon BJC 6000 Service Manual - Page 45

BJC-6000 Part 2: Product Specifications Host Ack (Input) When data is to be sent from the host computer to the printer, this signal is used to tell whether the data the host computer has output on the data bus is command or data ("L" means command and "H," data). In the reverse data transmission phase, this signal and Periph Clk perform handshaking. The host computer notifies the printer that it is ready to receive data by making this signal "L," and makes this signal "H" to notify that it has received the data. Reverse Req (Input) The host computer makes this signal "L" during a recovery process (re-sending data) in the forward data transmission phase. This signal goes "H" in response to the falling edge of Ack Reverse. The host computer also makes this signal "L" to notify the printer that the forward data transmission idle phase is to change to the reverse data transmission phase (data is to be sent from the printer to the host computer). Periph Req (Output) The printer makes this signal "L" to ask the host computer to change the forward data transmission phase to the reverse data transmission phase. When the host computer notifies the printer that the forward data transmission phase is to change to the reverse data transmission phase by making Reverse Req "L," the printer acknowledges by making both this signal and Ack Reverse "H." 1284 Active (Input) This signal goes "H" at the start of negotiation and is always "H" in ECP mode to indicate that bi-directional operation is in effect. When ECP mode is to be terminated, this signal goes "L" and termination phase is entered. 9) Timing charts 0.5us 0.5us 0.5us Min. Min. Min. DATA 1 to 8 STROBE BUSY ACKNLG 4us or 0.9us Figure 2-9 Timing Chart (Compatible mode) 2-15