JPH0422313B2 - - Google Patents

Description

[Detailed description of the invention]

[Overview] A unidirectional internal circuit, such as a first-in/first-out FIFO, is provided with a selector switch between the internal input/output port and the external port, enabling bidirectional data transfer within one chip, thereby reducing the mounting footprint. The aim is to reduce the size of the circuit and simplify the wiring. [Industrial Application Field] The present invention relates to a bidirectional semiconductor device that enables a unidirectional circuit such as a FIFO to perform bidirectional data transfer. [Prior art] In general, a two-port buffer (chip) such as a FIFO, last-in/first-out LIFO, or shift register has an input port and an output port, and allows unidirectional data transfer from the input port to the output port. Conventionally, each terminal corresponding to these input ports and output ports is fixed. For example, in the case of FIFO, as shown in Figure 6,
Write control signal is input to pin 1, input data IN
(I ₀ - I ₈ ) are sent to the 2nd - 6th pins and 24th - 27th pins, the read control signal is sent to the 15th pin, and the output data OUT (O ₀ - O ₈ ) is sent to the 9th - 13th pins and 16th
~ Fixed to pin 19. In addition, Vcc, Vss
indicates power supply, and other pins indicate full, empty, etc. When performing bidirectional data transfer using a unidirectional FIFO with fixed input and output pins as described above, two
Connect FIFO, and use FIFO for data transfer from A to B.
1, and on the other hand, for data transfer from B to A
This was done using FIFO2. [Problems to be Solved by the Invention] However, when the bidirectional device is configured as shown in FIG. 7, the mounting area on the printed board doubles due to the increase in the number of chips used, and /O) There was a problem that the wiring became complicated. It should be noted that the complication of the I/O wiring also causes a decrease in printed board mounting density due to an increase in the area occupied by the I/O wiring, and a deterioration of electrical characteristics due to an increase in the stray capacitance of the wiring. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bidirectional semiconductor device that reduces the mounting area on a printed board and simplifies I/O wiring. [Means for Solving the Problems] The present invention for solving the above-mentioned problems includes a unidirectional internal circuit having an internal input/output port for control signals and an internal input/output port for data signals; Four changeover switches each having a common terminal, a first terminal, and a second terminal are housed in one chip and includes an external port for control signals, an external port for data signals, and a mode switching port. tropic semiconductor device, the changeover switch has its common terminals connected to respective internal input ports for control signals, and a first terminal of the changeover switch connected to an external port and a second terminal of the changeover switch, The second terminal of the transfer switch is connected to the external port and the first terminal of the transfer switch, the common terminal of the transfer switch is connected to the internal input port for the data signal, respectively, and the first terminal of the transfer switch is connected to the external port and the first terminal of the transfer switch. The external port is connected to the second terminal of the selector switch, the second terminal of the selector switch is connected to the external port and the first terminal of the selector switch, and the common terminal of the selector switch is connected to a control signal to the mode selector port. The feature is that the connections to the first and second terminals are switched at the same time. [Operation] The operation of the bidirectional semiconductor device of the present invention configured as described above will be explained with reference to FIG. 1 only regarding data signals. When the switch SW is connected to the upper side of the diagram, data is transferred from the A side input/output terminal I/O (A) → internal circuit → B side input/output terminal I/O (B), and the switch SW When the connection is switched to the lower side of the diagram, data is transferred from the B-side input/output terminal I/O(B) to the internal circuit to the A-side input/output terminal I/O(A). [Embodiment] FIG. 2 is a circuit diagram showing an embodiment of a bidirectional semiconductor device according to the present invention. The dash-dotted line frame in FIG. 2 indicates one chip. This chip has only one unidirectional internal circuit, such as a FIFO.
has internal ports, IN, OUT, etc. In addition, external ports (A) and I/O (A) on the A side and external ports (B) and I/O (B) on the B side are provided around the chip for external connections. ing. And external port (A),
A first switch SW ₁ is provided between the W/R (B) and the internal port, and the external port (A),
A second switch SW ₂ is installed between (B) and the internal port.
A third switch SW ₃ is provided between the external ports I/O(A), I/O(B) and the internal port IN. A fourth switch _SW4 is provided between (B) and the internal port OUT. These switches _SW1 to _SW4 are operated simultaneously by the mode signal M. Note that the internal ports IN and OUT in Figure 2 are for data signals, and the external ports I/O(A) and I/O are for data signals.
O(B) is for a control signal, and actually has a multi-bit configuration, for example, 9 bits as shown in FIG. 6, but to simplify the explanation, it is assumed to have a 1-bit configuration. Each of the switches SW ₁ to _{SW 4} in FIG. 2 will be explained with reference to FIGS. 3A to 3D. As shown in FIG. 3A, the switch SW ₁ is composed of NAND circuits G ₁₁ , G ₁₂ , G ₁₃ and an inverter I ₁ , and therefore, when the mode signal M is “1”,
When W/R(A) is input to the write control port of FIFO, and on the other hand, mode signal M is “0”,
W/R(B) is input to the FIFO write control port. Similarly, as shown in Figure 3B, switch SW ₂
is composed of NAND circuits G ₂₁ , G ₂₂ , G ₂₃ and an inverter I ₂ . Therefore, when the mode signal M is “1”, (B) is input to the read control port of the FIFO, and on the other hand, the mode signal M When is "0", (A) is input to the read control port R of the FIFO. Similarly, as shown in Figure 3C, switch SW ₃
is composed of NAND circuits G ₃₁ , G ₃₂ , G ₃₃ and inverter I ₃ . Therefore, when mode signal M is “1”, I/O (A) is connected to the input data port IN of FIFO.
On the other hand, when the mode signal M is "0", I/O(B) is input to the input data port IN of the FIFO. In addition, as shown in Figure 3D, switch SW ₄
is composed of NAND circuits G ₄₁ , G ₄₂ , G ₄₃ , G ₄₄ , inverters I ₄ to I ₈ , and CMOS buffers BF ₁ and BF ₂ . Therefore, when the mode signal M is "1", the lower circuit in FIG. '', the upper circuit in FIG. 3D operates and the data at the output data port OUT is sent to the port I/O(A). To summarize the above,

〔Effect of the invention〕

As described above, according to the present invention, since the bidirectional semiconductor device is constituted by only one unidirectional circuit, the mounting area on the printed board can be reduced and the wiring can be simplified.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the bidirectional semiconductor device according to the invention, and Figs. 3A to 3D are details of the switch shown in Fig. 2. Logic circuit diagram, Figure 4 is the FIFO of Figure 2.
5 is a timing diagram for explaining the circuit operation of FIG. 4, FIG. 6 is an overview diagram showing a conventional unidirectional device, and FIG. 7 is a diagram of a conventional bidirectional device. FIG. FIFO...First-in/first-out (unidirectional circuit), IN, OUT,...Internal port, I/O...External port, SW ₁ to _{SW 4} ...
Switch.

Claims (1)

[Claims] 1. A unidirectional internal circuit FIFO having internal input/output ports W, R for control signals and internal input/output ports IN, OUT for data signals, a common terminal, a first terminal, and a first terminal. 4 changeover switches with 2 terminals
SW ₁ , SW ₂ , SW3, SW ₄ are connected to external ports W/R(A), W/R(B) for control signals and external ports I/O(A), I/O( B) is a bidirectional semiconductor device housed in one chip, and has a mode switching port M, and the switching switches SW ₁ and SW ₂ have common terminals connected to internal input ports W, for control signals, respectively. The first terminal of the changeover switch SW ₁ is connected to the external port W/R(A) and the second terminal of the changeover switch SW ₂ , and the second terminal of the changeover switch SW ₁ is connected to the external port W/R(A). /R(B) and the first terminal of the changeover switch _SW2 , and the common terminals of the changeover switches _SW3 and _SW4 are connected to internal input ports IN and OUT for data signals, respectively.
The first terminal of the changeover switch _SW3 is connected to the external port I/O(A) and the second terminal of the changeover switch _SW4 , and the second terminal of the changeover switch _SW3 is connected to the external port I/O(A). O(B) is connected to the first terminal of the changeover switch _SW4 , and the common terminal of the changeover switches _SW1 , _SW2 , SW3, _SW4 is connected to the first and second terminals at the same time by a control signal to the mode changeover port M. A bidirectional semiconductor device characterized in that connection to a terminal is switched.