Epson 500 manual 140

Pin no.		Signal name	GND	In/Out	Description
10		PtrClk	28	Out	Used to qualify data
					being sent to the host.
					Set LOW then HIGH to
					cause an interrupt
					indicating to host that
					data is available.
11		PtrBusy/	29	Out	Data bits 3 then 7
		DataBit-3,7			indicate forward
					channel busy status.
12	ACkDataReq/		28	Out	Data bits 2 then 6. Set
		DataBit-2,6			HIGH until host requests
					data transfer, then
					follows nData Avail
					(nFault).
13		Xflag/	28	Out	X-flag signal and reverse
		DataBit-1,5			channel transfer data
					bit 1 then 5
14		HostBusy	30	In	Set LOW to indicate that
					host can receive
					peripheral device to
					host data. Then set high
					to acknowledge receipt
					of that nibble. Set high
					in response to PtrClk
					(nAck) low pulse to
					re-enter reverse data
					transfer phase.
31			30	In	Not used.
		INIT
32			29	Out	This signal is LOW when
		DataAvail/
		DataBit-0,4			the printer is in an error
					state.
36	1284-Active		30	In	1284 active signal
18		Logic H	-	Out	Pulled up to +5V
					through 3.9 kΩ
					resistance.
35		+5V	-	Out	Pulled up to +5V
					through 3.3 kΩ
					resistance.
17		Chassis	-	-	Chassis GND.

Technical Specifications A-13