7
3. Interfaces
3.1 Parallel interface (Centronics) (if requested)
1) Data input method: 8 bit parallel method (Data0 ~ data7)
2) Control signal: /ACK, BUSY, -STB, -ERROR, PE, SLCT, /INIT
3) Input signal to printer
Data 0 ~ data 7: 8 bit parallel signal (positive theory: PT)
/STB: Signal to read 8 bit data (negative theory: NT)
/INIT: Signal to reset whole printer (NT)
4) Printer output signal
/ACK: Last output pulse signal of busy signal at 8 bit data request signal (NT)
BUSY: Signal to indicate printer busy status and it inputs new data at “LOW” (PT)
/ERROR: Signal to become “LOW” at printer’s alarm status. All control circuit stops (NT)
PE: Output signal at no paper status (PT)
SLCT: Signal to indicate on-line status (PT)
5) Input/output signal conditions
Abbr.
Min. Typ. Max.
Unit
Input LOW level voltage
V IL
0
-
0.18Vcc
V
Input HIGH level voltage
V IH
0.7Vcc
-
Vcc
V
Output LOW level voltage
V OL
-
-
0.7
V
Output HIGH level voltage
V OH
0.7Vcc
-
-
V
6) Input/output circuit
VCC
VCC
74LV574
STROB
PD0~PD7
ACK, P E, SLCT, ERROR
BUSY
INIT IN
OUT PUT
OUT PUT
IN PUT
IN PUT
IN PUT
3.3K
100
470p
3.3k
3.3K
74LV14
74LV14
47
74LV32
47
1SS319
510
