interfacciamento porta parallela
DESCRIPTION
Interfacciamento porta parallela. e primi esempi in Java Alessandro Memo. Some basics of a parallel port. - PowerPoint PPT PresentationTRANSCRIPT
Interfacciamento porta parallela
e primi esempi in Java
Alessandro Memo Alessandro Memo
Some basics of a parallel port
A port contains a set of signal lines that the CPU sends or receives data with other components. We use ports to communicate via modem, printer, keyboard, mouse etc. In signaling, open signals are "1" and close signals are "0" so it is like binary system. A parallel port sends 8 bits and receives 5 bits at a time, with the use of three different registers.
Some basics of a parallel port
Thus it is often called as printer Port or Centronics port (this name came from a popular printer manufacturing company 'Centronics' who devised some standards for parallel port). You can see the parallel port connector in the rear panel of your PC. It is a 25 pins female (DB25) connector (to which printer is connected). On almost all the PCs only one parallel port is present.
Some basics of a parallel port
The IEEE 1284 Standard which has been published in 1994 defines five modes of data transfer for parallel port. They are:
1) Compatibility Mode 2) Nibble Mode 3) Byte Mode 4) EPP 5) ECP
Typically, we’ll use only Compatibility Mode.
D0
12345678910111213
141516171819202122232425
D1D2D3D4D5D6D7S7S6S5S4S3S2S1S0
C7C6C5C4C3C2C1C0
DATA PORT
CONTROL PORT
STATUS PORT
Some basics of a parallel port
The parallel portcontains three groups of bits:
• data bits (D0-D7)
• status status (S3-S7)
• control bits (C0-C3)
• and ground bits (18-15)and ground bits (18-15)
GND
Parallel Port – Data bits
The old PC has LPT parallel port function only for sending data. Many devices nowadays have attached to this port and can work bidirectional (ECP and EPP mode).Data Port can sink 24 mA at logic 0 and can source 2.6 mA at logic 1. Notice that the external device don't try to pull these DP lines to ground for a long period. The latch IC could be burn.
pin num
BIT SIGNAL NAME
INPUT OUTPUT
DATA PORT
0x0378
9
8
7
6
5
4
3
2
D7
D6
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
These bits may be input, but all you
will get is the value
currently residing in the output latch, unless the interface is
genuinely bi-directional
Latched TTL push-
pull outputs
with 2.2nF slow-down capacitors
Parallel Port – Data bits
Parallel Port – Status bits
Status Port use for feedback signal from printer to the computer. Only 5 MSB bits are used and accessible.Only 1 bit is inverting input, ie. S7, use for busy signal. S6 bit use for acknowledge signal, this signal used when the printing goes on with interrupt handshake operation. This is a hardware interrupt. In some PC/AT's card and bi-directional card, S2 is used to reflex the state of IRQ, weather it is on or off state. This bit only for internal use.
pin num
BIT SIGNAL NAME
INPUT OUTPUT
STATUS PORT
0x0379
11
10
12
13
15
na
na
na
S7
S6
S5
S4
S3
S2
S1
S0
BUSY
ACK
PAPER_OUT
SELECT
ERROR
IRQ
not available
not available
TTL inputs
no pull-up
resistor
not available
not available
not available
not available
not available
not available
not available
not available
not available
not available
not available
Parallel Port – Status bits
Parallel Port – Control bitsControl Port is used for controlling the function of printer. Only 4 bits used by printer and 1 bit used for interrupt enable flag. The most important things must be taken if you connect your own device are : the C0, C1 and C3 logic are inverting at socket connector terminal. This means that, when you send logic 1 (high) to this related bit, the logic output terminal is 0 (low). The C2 and C4 are normal. Note that, C4 bit only for the adapter card function.
Parallel Port – Control bits
pin num
BIT SIGNAL NAME
INPUT OUTPUT
CONTROL PORT
0x037A
na
na
na
na
17
16
14
1
C7
C6
C5
C4
C3
C2
C1
C0
not available
not available
DIRECTION
IRQ ENABLE
SLCT IN
INIT
LINE FEED
STROBE
not available
not available
not available
not available
may be used as inputs if
corresponding output bits are set to "1
not available
not available
not available
not available
open collector
output with 4.7K pull-up resistor and 2.2nF slow-
down capacitor
Besides that, in some PC/AT's LPT adapter card, bit C5 is used for control direction (and also in bi-directional card). It means that, if this bit is high, Data Port can act as input port, the latch output is tri-state. Data from outside can be read from Data Port.Control Port can sink 7 mA at logic 0 and can source 0.6 mA at logic 1.
Parallel Port – Control bits
Standard Interface Description
LPT printer parallel interface in PC computer type have specification like this :
• Data transfer rate : 1000 cps (maximum)• Synchronization : by externally-supplied
STROBE pulses.• Handshaking -ACK or +BUSY signals.• Logic level : input data and all interface
control signal are compatible with the TTL level.
Standard Interface Description
Checking LPT Installed
In a new card (bidirectional card), simple send a byte to DP port and then read back again. If the result was not an FF Hex or if the result exactly the same to the byte wrote, then the card is installed at that port. This happened because, if the card not installed, the accessing port is a tri-state all, there is no connection to the hardware logic. Tri-state logic interpreted as logic 1.
Software - Java1. Predisporre una cartella per ogni applicazione
che si intende sviluppare, e copiare al suo interno i file pPort.class e ioPort.class
2. Copiare (se non è già presente) il file jnpout32pkg.dll nella cartella C:\WINDOWS\system32, oppure in alternativa copiarlo nella cartella dell’applicazione
3. Inserire nel programma la direttiva
import jnpout32.*;
import jnpout32.*; // interfacciamento alla DLL
public class minimo{
static short dato; // variabili di classestatic short indirizzo;static pPort lpt;
public static void main ( String args[ ] ) {
lpt = new pPort (); // istanza di una nuova porta
indirizzo = 0x378; // indirizzo Data Port LPT1
dato = 0x77; // un dato qualsiasi
lpt.output (indirizzo,dato); // scrivo il datoSystem.out.println ("Scrittura nel Port: " +
indirizzo + " del dato: " + dato);
dato = (short) lpt.input (indirizzo); // leggo il dato
System.out.println ("Lettura dal Port: " + indirizzo +
" del dato: " + dato);}
}
Methods of class pPort :
ParallelPort output method:public void output (short port, short
value)
ParallelPort input method: public short input (short port)
Set all bits on Data port to zero: public void setAllDataBits (short
value)
Set PinNumber <pin> to <value>: public void setPin (short pin, short
value)
Definition and declaration of port:pPort <MiaPorta> = new
pPort();
Extension of methods of class pPort :
Set Data Bit at selected index to a value of 1 or 0while preserving current values of all other Data bits:
public void setDataBit (short index, short value)
Set Control Bit at selected index to a value of 1 or 0while preserving current values of all other Control bits:
public void setControlBit (short index, short value)
Get Status Bit at selected index to a value of 1 or 0:public void GetStatusBit (short index, short
value)
NB: attention to the type (short) !!!
dato_in = ((<MiaPorta>.input(STATUS_PORT)^0x80) >> 3);
The bi-directional card used bit C5 to control the direction of data in Data Port. If the C5 bit is low, the Data Port act as output port and if it is high, the Data Port is used for input port. When the Data Port act as output port, the data is latch at the output, so if we read this data back from the Data Port, the data must always the same as that we send. But if Data Port act as input port, the read data must be FF Hex, because the latch of Data Port is in tri-state.
Checking LPT Bi-directional
Esercizi riepilogativi
1. Leggere lo stato di tutti i tasti2. Individuare lo stato di un solo tasto (bit
S6)3. Accendere e spegnere dei LED (Data
Port) 4. Ruotare i LED con una frequenza di 1
secondo5. Ruotare i LED fino alla pressione di un
tasto particolare6. Accendere e spegnere tutti i LED del
Data Port seguendo sequenze prestabilite associate ai vari tasti (proposto)