6-3
ST78C34
PLCC Package
GENERAL PURPOSE PARALLEL
PRINTER PORT WITH 83 BYTE FIFO
DESCRIPTION
The ST78C34 is a monolithic Bidirectional Parallel
port designed to operate as a general purpose I/O port.
It contains all the necessary input/output signals to be
configured as a CENTRONICS printer port.
The ST78C34 is a general purpose input/output con-
troller with 83 byte internal FIFO. FIFO operation can
be enabled or disabled. For CENTRONICS printer
operation, all registers are mapped to IBM printer port
registers.
The ST78C34 is designed to operate as normal
printer interface without any additional settings. Con-
tents of the FIFO will be cleared after reset or setting
the INIT pin to a low state. The auto FIFO operation
starts after the first -ACK is received from the printer.
Contents of the FIFO transfer to the printer at the
printer loading speed.
FEATURES
· 83 bytes of printer output FIFO
· Bi-directional software parallel port
· Bi-directional I/O ports
· Register compatible to IBM XT, AT, compatible
386, 486
· Selectable interrupt polarity
· Selectable FIFO interrupts
ORDERING INFORMATION
Part number Pin Package Operating temperature
ST78C34CJ44 44 PLCC 0° C to + 70° C
ST78C34CP40 40 PDip 0° C to + 70° C
ST78C34IJ44 44 PLCC -40° C to + 85° C
ST78C34IP40 40 PDip -40° C to + 85° C
Rev. 3.00
6
5
4
3
2
1
44
43
42
41
40
7
8
9
10
11
12
13
14
15
16
17
39
38
37
36
35
34
33
32
31
30
29
18
19
20
21
22
23
24
25
26
27
28
N.C.
INTSEL
D7
D6
D5
D4
D3
D2
D1
D0
N.C.
N.C.
INT
XTAL1
XTAL2
-CS
GND
RESET
-STROBE
-AUTOFDX
INIT
-SLCTIN
N.C.
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
GND
N.C.
N.C.
PE
-ACK
BUSY
SLCT
-ERROR
VCC
-IOR
-IOW
A1
A0
ST78C34CJ44
