Multiplex communications – Channel assignment techniques – Details of circuit or interface for connecting user to the...
Reexamination Certificate
1998-12-02
2004-05-25
Ton, Dang (Department: 2661)
Multiplex communications
Channel assignment techniques
Details of circuit or interface for connecting user to the...
C370S429000, C370S412000
Reexamination Certificate
active
06741606
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication control apparatus for performing two-way communication processing with a data processing apparatus via a predetermined interface, a method for processing data of the communication control apparatus, and a storage medium storing programs capable of being read by a computer.
2. Description of the Related Art
Conventionally, data communication between a host apparatus and an image input/output apparatus, such as a printer, a scanner or the like, is executed via a predetermined interface. A Centronics interface, serving as an interface of this type, is a main interface for transferring data from a host computer to a printer, and has the feature that inexpensive high-speed data transfer can be performed with standards for transmitting data from a computer to a printer which have been developed by Centronics Corporation of U.S.A. for its own printers. Although the Centronics interface is widely used as means for transmitting data from a personal computer (PC) to a printer, it is not standardized.
Although the Centronics interface has many variations depending on each combination of a host computer and a printer, the variations are basically similar. Basic controls are performed using three signal lines, i.e., DATA STROBE, ACK and BUSY. A transfer method using these three signal lines is called a compatibility mode in contrast to a nibble mode, a byte mode, an ECP (extended capabilities port) mode and the like (to be described later).
The compatibility mode will now be described in detail with reference to drawings. It is impossible to describe all of many variations which exist in the compatibility mode as described above. Hence, a description will be provided illustrating a laser-beam printer made by Canon Inc.
FIG. 22
is a plan view illustrating the pin arrangement of a printer interface in a printing system to which a communication control apparatus of this type can be applied. In
FIG. 22
, 36 pins are arranged.
Numerals in
FIG. 22
represent the numbers of respective pins, each of which corresponds to one signal line. In
FIG. 22
, a pin
1
is a signal line for DATA STROBE, and usually assumes a “High” state. When the state shifts to a “Low” state, a printer reads the states of pins
2
-
9
for data lines DATA
1
-DATA
8
, respectively.
The data lines DATA
1
-DATA
8
represent information for the 0th-7th bits, respectively, of data transmitted from a host apparatus. On each of these data lines, data is “1” and “0” in the “High” and “Low” states, respectively. In a stationary state, data is indefinite. Data is effective only when the DATA STROBE line assumes the “Low” state.
A pin
10
is for an acknowledge line ACK, and assumes the “High” state in a stationary state. A pulse for providing the “Low” state is generated when the state shifts from the stationary state.
A pin
11
is for a busy line BUSY, on which a state signal indicating whether or not the printer can receive data from the host apparatus is provided. On this line, the “Low” state represents a state in which a signal can be received, and the “High” state represents a state in which a signal cannot be received.
A pin
12
is for a printer error line PE, which assumes the “High” state when an error is generated in the printer, and assumes the “Low” state in other states. A pin
13
is for a select line SELECT, which assumes the “High” state when the printer is in an on-line state, and assumes the “Low” state in other states. A pin
14
is for a signal line AUTO FD, which is unused.
A pin
15
is for a signal line AUXOUT
1
, which always assumes the “High” state. The ground level of the printer is applied to a pin
16
. A pin
17
is for a frame ground line Frame GND, which corresponds to the frame ground of the printer.
A voltage of +5 V is applied to a pin
18
, which always assumes the “High” state. Pins
19
-
30
are connected to the ground. A pin
31
is for an input prime line INIT, which always assumes the “High” state. By making the input prime line INIT to the “Low” state, input prime processing is performed.
A pin
32
is for a signal line FAULT, which assumes the “High” state when the printer is in an on-line state, and assumes the “Low” state in other states. A pin
33
is for a signal line AUXOUT
2
, which always assumes the “Low” state. A pin
34
is for a signal line AUXOUT
3
, which always assumes the “Low” state. A pin
35
is for a signal line AUXOUT
4
, which always assumes the “High” state. A pin
36
is for a signal line SELECTIN, which is unused.
In the compatibility mode, the pins
1
-
11
for DATA STROBE, DATA
1
, DATA
2
, DATA
3
, DATA
4
, DATA
5
, DATA
6
, DATA
7
, DATA
8
, ACK and BUSY, respectively, are mainly used.
FIG. 23
illustrates handshaking in the compatibility mode.
FIG. 23
illustrates a timing chart for explaining the state of data transfer processing in the printing system. The timing chart shown in
FIG. 23
corresponds to handshaking in the compatibility mode. In this case, 1-byte data is transmitted.
The compatibility mode can only perform data transfer in one direction from the host apparatus to the printer, and cannot perform data transfer from the printer to the host apparatus.
In order to solve this problem, two-way Centronics communication handshaking is standardized by the IEEE (Institute of Electrical and Electronics Engineers) as a superior alternative of the compatibility mode (IEEE 1284-1994).
In the IEEE 1284-1994, a plurality of communication modes, such as the nibble mode, the byte mode, the ECP mode and the like, are newly provided in addition to the above-described compatibility mode (the conventional handshaking for transferring data from a host apparatus to a printer).
Connectors and cables having the same shape as in the compatibility mode can be used in all of the newly added modes. The nibble mode is for transferring data from a printer to a host apparatus. By alternately using the nibble mode and the compatibility mode, two-way communication between a host apparatus and a printer can be realized.
That is, by performing transmission from a host apparatus to a printer in the compatibility mode and performing transmission from the printer to the host apparatus in the nibble mode, two-way communication can be realized.
In the nibble mode, control is performed using the acknowledge signal line ACK and the signal line AUTO FD, and data is set on the four signal lines, i.e., BUSY, PE, SELECT and FAULT.
8-bit (1-byte) transfer is realized by dividing 1 byte of data into two 4-bit portions, and first transmitting lower-order 4 bits followed by transmission of higher-order 4 bits. The signal line FAULT is also used for indicating by the printer whether or not data to be transmitted to the host apparatus is ready at a specific timing. Handshaking is performed without using the signal lines DATA
1
, DATA
2
, . . . , DATA
8
which are controlled only by the host apparatus in the compatibility mode. These signal lines DATA
1
, DATA
2
, . . . , DATA
8
are called data buses. Since the data buses are not used in the nibble mode, the host apparatus side need not provide hardware for dealing with data transmitted through the data buses. Hence, mounting can be relatively easily realized.
The byte mode is also for performing communication from a printer to a host apparatus, as the nibble mode. By alternately using the compatibility mode and the byte mode, two-way communication between the host apparatus and the printer can be realized.
That is, by performing transmission from the host apparatus to the printer in the compatibility mode, and performing transmission from the printer to the host apparatus in the byte mode, two-way communication can be realized. In the byte mode, control is performed using the signal lines STROBE, ACK, BUSY, PE, AUTO FD and FAULT, and data is set on the data buses (the signal lines DATA
1
, DATA
2
, . . . , DATA
8
). This mode is more efficient than the nibble mode because 1-byte (8-bit) data is simultaneously transmitted. However, sin
Phan Tri H.
Ton Dang
LandOfFree
Interface control apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Interface control apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interface control apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3260045