JPH03250784A - Printed circuit board for using sram's in common - Google Patents

Abstract

PURPOSE:To use SRAM's in common by forming the same number of terminal hole as that of the terminals of a larger capacity SRAM on a printed circuit board, using ground terminal holes for smaller and larger capacity SRAM's in common and forming a printed circuit to which resistors are mounted in the neighborhood of spaces between the terminal holes which are not required when the smaller capacity SRAM's are mounted. CONSTITUTION:The same number of terminal holes 8 as that of the terminals of larger capacity SRAM's are formed on a printed circuit board 11. A printed circuit uses ground terminal holes for smaller and larger capacity SRAM's in common. The power supply terminal holes of the smaller and the larger capacity SRAM's are connected to one another. The WE terminals of the smaller and the larger capacity SRAM's are connected to each other via a first resistor 9. The resistor 9 is mounted in the neighborhood of a space between the terminal holes which become unnecessary so as to prevent a wrong mounting when the smaller capacity SRAM is mounted. The WE terminal of the smaller capacity SRAM is formed so as to be connected to the power supply terminal hole via a second resistor 10. Thus, printed circuit boards of a plurality of kinds are not required to be prepared in accordance with the SRAM's with different memory capacities and different number of the terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a printed circuit board for SRAM sharing that allows a large capacity SRAM to be installed instead of a small capacity SRAM.

[Prior Art] Printed circuit boards equipped with a large number of SRAMs are often used in general electronic devices and systems.

Figures 4 to 6 show 16 bits (2048 words x 8 bits configuration), 64 bits (8192 words x 8 bits configuration), and 256 bits (327688i!iX8 bits configuration) mounted on the printed circuit board, respectively. SRAM of
This is a layout diagram of the terminals (bins) of (Static Random Access Memory) viewed from the top side, with the terminal number written on each terminal and its function added. In FIGS. 4 to 6, fl) is 1.6 Kbit SRAM (hereinafter referred to as 16
KsRAM), (2) is 64-bit SRAM
(hereinafter referred to as 64KSRAM) 13) is a 256-bit SRAM (hereinafter referred to as 256KSRAM),
(41 is a terminal, and in the case of 16KSRAM+11, 2
Connect the four terminals to 64KSRAMf21 and 256KS
RAM (3) has 28 terminals.

(5) is the power supply (battery backup power supply), 16
1 indicates GND (ground), and (7) indicates a capacitor.

Next, the symbols indicating the role (function) written together with the terminal number for each terminal (]O0 will be explained. AO to A15 are address bus terminals, l101 to r108 are data bus terminals for data input/output, and OE is a read command. A signal terminal, WE is a write command signal terminal, CS is a chip select terminal, CS, CS2 in FIG. 5 are the first and second chip select terminals, respectively, VCC is a power supply terminal, Vs
s indicates a ground terminal. 16KSRAM (1+ and 64KS
RAM (2) and 256 K S RAM [31
The number of terminals is different from 64K SRAM [
2) and 256KSRΔM(3) have the same number of terminals, 28, but if the role of the terminal is one example, terminal numbers 1 and 2 are used.
0.26 is different. However, the terminals and the dimensions between the terminals are standardized for each S' RAM (2) and 1 (for example, 256 KS RAM (31) in the terminal hole of the printed circuit board for mounting 64 K S RAM (2) and 1).
(3KSRAMf1.l can be installed.

L Problem to be solved by the invention J Since the number of terminals of an SRAM and the role of each terminal generally differ depending on the memory capacity, the above SRΔM on the printed circuit board is
During the installation process, if the required memory capacity of 8 degrees is not available, use the Hitoyoshi FI with a larger memory capacity.
Even if you want to use sRAM as a substitute, it cannot be installed on a conventional printed circuit board, and it is difficult to install it on a conventional printed circuit board.
There were problems such as the need to prepare multiple types of printed circuit boards for AM.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a printed circuit board for SRAM sharing that allows a large-capacity SRAM to be installed instead of a small-capacity SRAM.

[Means for Solving the Problems] The printed circuit board for SRAM sharing according to the first invention is capable of mounting a large-capacity SRAM with a different number of terminals in place of the Kokichi 1tsRAM. A hole is formed between the small capacity SRAM and the large capacity sR.
It shares the ground terminal hole with the AM and connects the respective power supply terminal holes, and the WE terminal hole of the Kokichi llSRAM is connected to the WE terminal hole of the Daikan jlisRAM through the first resistor, and the WE terminal hole of the Kokichi In order to prevent incorrect installation when installing fISRAM, the above-mentioned first
I installed the resistor of 2, and the above Kokichi 1 is RAM WE
The terminal hole should be connected to the power supply terminal hole via the second resistor (printed wiring is formed).

Further, the printed circuit board for SRAM sharing according to the second invention has a ground terminal between the small capacity SRAM and the large capacity SRAM, so that a large capacity SRAM having the same number of terminals can be installed instead of the Kokichi IsRAM. hole and power supply terminal hole, and the NC terminal hole of the small capacity SRAM is connected to the ground terminal hole, and if the Kokichi fiSRAM has two O3 terminals, the first The C5 terminal hole is the common C5 terminal hole of the SRAM, and a printed wiring is formed to connect the second C5 terminal hole of the Kokichi JiSRAM to the terminal hole.

[Function] The terminal hole of the printed circuit board in the first invention has a large capacity SR.
The printed wiring is formed to match the number of AM terminals, and the printed wiring shares the ground terminal hole of the Kokichi ffi: S RAM and the above-mentioned large-capacity S RAM, connects the respective power terminal holes, and connects the WE terminal of the above-mentioned Kokichi 1isRAM. is connected to the WE terminal of the large-capacity SRAM through the first resistor, and the first resistor is located near the terminal hole which becomes unnecessary in order to prevent incorrect installation when the Kokichi ffi SRAM is installed. is installed, and the WE terminal of the writer jlsRAM is formed to be connected to the power supply terminal hole via a second resistor.

Further, the printed wiring of the printed circuit board in the second invention shares the ground terminal hole and the power supply terminal hole of the Bokukyu jltsRAM and the Daikichi jlSRAM, and also shares the ground terminal hole and the power terminal hole of the Bokukyu tsR.
The NC terminal hole of the AM is connected to the grounding terminal hole, and when the above-mentioned customer 1tSRAM has two C8 terminals, the terminal hole of the first CS terminal common to the above-mentioned large capacity SRAM is connected to the common O5 of the above-mentioned SRAM. With the terminal hole, the above writer fiSR
A second C8 terminal hole of the AM is formed to connect with the power supply terminal hole.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In the figure, the same reference numerals as in the conventional example indicate the same or equivalent elements in the conventional example.

Figure 1 shows 16KSRAM [256KS instead of 1,l]
The circuit diagram of the printed circuit board (11) for SRAM sharing on which RAM CS1 is installed, Figure 2 is 16KSRA.
FIG. 3 is a diagram showing a part of the external appearance showing the mounting state of M m.

In FIG. 1, (8) is a terminal hole for mounting an SRAM formed on a printed circuit board (11), which will be described later, and the symbols T1 to 728 attached to each terminal hole are 256KSRΔM (3).
Indicates the terminal number when installed. 1 For example, T 3 (11 < The number in parentheses is 16 K S RAM (
Indicates the terminal number when 11 is installed, (9) is 16 and 256
Resistor for switching the write command signal of KSRAM (11, (31), (lO) is All when 256KSRAM is installed.
This is a pull-up resistor to establish the terminal at "H" level.

Next, 1.6 K and 256 K S RA, M (11, (
3) The shared circuit and mounting method will be explained. 16Ks
RAM f1+ has bins 1, 12, 13, and 24 as 2
56 K S RAM (3) 3.14.15.2
Implement it to correspond to the 6th bin. In this case, the pin assignments do not match 256 K S RAM T3
) for Al1, , A1.2 of G N D (61
Confirm the address by connecting to. Regarding the WE terminal which is the write command signal terminal, 16KsRAM [1
When installing 1, a resistor (9) is mounted, and 256KSRAM
(3) At the time of mounting, the input source of the write command signal is switched by not mounting the resistor (9).

Resistor (10) is resistor (9) when 256KSRAM is installed.
This was inserted to prevent terminal All from becoming unstable because it is not mounted. Also, the mounting position of the resistor (9) is set at 1.2 of the 256KSRAM as shown in Figure 2.
By placing it between the No. 27 and 28th bins, 16
Preventing incorrect mounting with 256KSRAM, e.g. 16K
Preventing gaps in SRAM+lj mounting terminal holes or 16Ks
256 K S RAM (3) instead of RAM (1)
) and erroneous switching of the write command signal due to whether or not the resistor (9) is mounted. For example, when a 16KSRAM is mounted, it will not operate without the resistor (9), which can be confirmed at the time of shipment. Furthermore, the presence of the resistor (9) makes it impossible to mount the 256KSRAM, making it possible to prevent incorrect mounting during assembly.

Figure 3 shows 25 instead of 64 K S RAM (2).
FIG. 2 is a circuit diagram of a printed circuit board for SRAM sharing on which a 6KS RAM [3] is installed. In the figure, (
121 is an NA for controlling the depth select signal to select either the first or second chip select signal when the 64 K S RAM +21 is installed.
The ND gate (13) is an impeller that inverts the input signal.

Next, the 64 and 256 KSRAM shared circuit will be explained. 64KSRAMf2) and 256KSRAMM+
As shown in Figure 3, the differences between the 1st bin and the 26th bin +j of 31 are GND (6) and power supply (5
) to confirm the address. 64K
When SRAM selection is performed using both chip select signals 1 and 2, the chip select signal 1 is inverted by an inverter (13), NANDed with chip select signal 2, and input to the 20th bin. R.A.
Let M be selected.

In the above embodiment, in order to determine the address, in the 16/256KSRAM shared circuit shown in FIG.
Connect A14 (bin 1 of 256KSRAM) to GND in the 64/256KSRAM shared circuit shown in Figure 3.
However, the A12 and A14 address terminals are connected to 2.
It is also possible to determine the address by pulling up to a potential of 2 [V] or higher.

In addition, in the 16/256KSRAM shared circuit, the input light of the write command signal is changed and a resistor (9) is used to prevent incorrect mounting of the 16KSRAM, but it is possible to replace this with a component such as a shorting piece. is also possible. Furthermore, in the 64/256KSRAM shared circuit, if SRAM selection is performed using only either chip select signal 1 or 2, the 26th bin is connected to the power supply,
It is also possible to connect the controlling chip select signal to the 20th bin.

[Effects of the Invention] As described above, according to the first invention, terminal holes as many as the number of terminals of a large SRAM are formed on a printed circuit board.

The ground terminal hole of the JilSRAM and the above-mentioned large capacity sRAM is shared, and the WE terminal hole of the isRAM is connected to the WE terminal hole of the large-capacity ftsRAM through the first resistor, and the According to the second invention, the first resistor is installed in the vicinity of the terminal holes that are unnecessary when installing the resistor. If the small-capacity SRAM has two O3 terminals, a printed wiring is used to connect the second CS terminal hole of the small-capacity SRAM to the power terminal hole. Since this structure is formed, there is an effect that there is no need to prepare a plurality of types of printed circuit boards for each SRAM having a different memory capacity and number of terminals.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a printed circuit board for SRAM sharing in which a 256KSRAM is installed instead of a 16KSRAM according to an embodiment of the present invention, FIG. 2 is an actual wiring diagram of the circuit diagram shown in FIG. Figure 3 shows 2 instead of 64KSRAM.
Circuit diagrams of printed circuit boards for SRAM sharing on which 56KSRAMs are mounted, Figures 4 to 6 are circuit diagrams of SRAMs on conventional printed circuit boards.
64 is a circuit diagram of a 256KSRAM. In the figure, [1] to (3) are 16K, 64, and 256KSRAM, respectively, (4) is the terminal of each SRAM, and (8
) are the terminal holes of the printed circuit board (10), (91, (101)
is a resistor, (12) is a NAND gate element, and (13) is an inverter element. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) Large capacity S with different number of terminals instead of small capacity SRAM
The terminal holes are formed to have the same number of terminals as the large-capacity SRAM, so that the RAM can be attached to the small-capacity SRAM and the large-capacity SRAM.
The WE terminal hole of the small capacity SRAM is connected to the WE terminal hole of the large capacity SRAM via the first resistor, and the WE terminal hole of the small capacity SRAM is connected to the WE terminal hole of the large capacity SRAM through the first resistor. In order to prevent incorrect installation when installing the capacity SRAM, the first resistor is installed near unnecessary terminal holes, and the WE terminal hole of the small capacity SRAM is connected to the power supply through the second resistor. A printed circuit board for common use with an SRAM, characterized in that printed wiring is formed to connect terminal holes. (2) Large capacity S with the same number of terminals instead of small capacity SRAM
RAM can be attached to the above small capacity SRAM and above large capacity S
In addition to sharing the ground terminal hole and power supply terminal hole with the RAM, the NC terminal hole of the small capacity SRAM is connected to the ground terminal hole, and if the small capacity SRAM has two CS terminals, the NC terminal hole of the small capacity SRAM is connected to the ground terminal hole of the small capacity SRAM. A first CS terminal hole common to the SRAM is a CS terminal hole common to the SRAM, and a printed wiring is formed to connect the second CS terminal hole of the small capacity SRAM to the power supply terminal hole. SR to do
Printed circuit board for AM sharing.