Ack, Busy, /Stb, /Error, Pe, Slct, /Init

3.Interface specifications

3.1 Parallel interface (Centronics)

1) Data input		: 8 bit parallel method(DATA 0 – DATA 7)
2) Control signals		: /ACK, BUSY, /STB, /ERROR, PE, SLCT, /INIT
3) Input signal to a printer
DATA 0 – 7		: 8 bit parallel signal(positive logic)
/STB		: Signal to read 8 bit data(negative logic)
/INIT		: Signal to reset an entire printer(negative logic)
/LF		: Signal to feed paper to print mechanism(negative logic)
4) Output signal from a printer
/ACK		: Enquiry signal for 8 bit data. It’s also pulse signal which is output after
		BUSY signals (negative logic)
BUSY		: Indicate BUSY status of the printer. Inputs new data at LOW status
		(positive logic)
/ERROR		: This signal becomes LOW when a printer is in the alarm status.
In the LOW status, all control circuits in the printer stops (negative logic)
PE		: Outputs when roll paper becomes empty (positive logic)
SLCT		: Signal to indicate on-line status (positive logic)
5) Input/Output signal level
			Code	Standard value			Unit
			Code	Min.	TYP.	Max.	Unit
				Min.	TYP.	Max.
	Input low level		VIL	-	-	0.18Vcc	V
	Input high level		VIH	0.7Vcc	-	-	V
	Output low level		VOL	-	-	0.7Vcc	V
	Output high level		VOH	0.7Vcc	-	-	V
*IOL4mA

6) Input/Output conditions

74LV574

VCC

3.3K

100

74LV14

470p

VCC

3.3K

STROB IN PUT

VCC

10K

3.3k	PD0~PD7
	IN PUT