JPH02297234A - Internal/external rom switching device for single chip microcomputer - Google Patents

Abstract

PURPOSE:To reduce the soft changing cost by providing a connection part on a bus line set between a circuit to be controlled and a single chip microcomputer, causing a short-circuit with a jumper line in a normal control state, and attaching an external ROM in response to the soft change. CONSTITUTION:When a jumper part 2-1 is mounted to the connection parts 5A and 5B, a terminal 8 is earthed and an L signal is generated at the terminal 8. The L signal actuates the internal ROM 6 of a single chip microcomputer 1. Then an external ROM unit 2-2 is mounted on both parts 5A and 5B in place of the part 2-1. Thus the terminal 8 is opened and an H signal is generated at the terminal 8. The signal H stops the operation of the ROM 6. Simultaneously, the EPROM 7 of the unit 2-2 is actuated and a control signal is sent to a circuit 3 to be controlled via a PIO 12.

Description

[Detailed Description of the Invention] [Summary] The present invention provides two connection parts in the middle of a bus line that connects a single-chip microcomputer and a controlled circuit, and connects two connection parts between two connection parts. A switching device between an internal ROM and an external ROM of a single-chip microcomputer that selectively connects a jumper unit that directly connects the ROM and an external ROM unit that includes an external ROM that is switched from the internal ROM of the single-chip microcomputer, You can reduce the cost of changes.

[Industrial application field]

The present invention relates to a single-chip microcomputer.

Single-chip microcomputers are used as control microcomputers for many products, and programs are written into a ROM within the chip in the form of a mask. The present invention refers to a method of switching between an internal ROM and an external ROM of a single-chip microcomputer.

[Conventional technology]

FIG. 6 is a diagram illustrating control using a single-chip microcomputer based on the conventional ROM built-in system.

The configuration of this figure will be explained below. Note that similar components are represented by the same reference numbers or symbols throughout the drawings. In this figure, single-chip microcomputer 1 is a CPU
10 other life masked 1 in O gate 6, R
It is equipped with AM 11 and PIo 12. The controlled circuit 3 is a typical circuit controlled by the single-chip microcomputer 1. Next, the operation will be explained.

Arithmetic and logical operations are performed based on instructions retrieved from the ROM 6 by Cl1tl to in the single-chip microcomputer l. The obtained results are temporarily held in the RAM 11 and transmitted to the controlled circuit 3 via the Plo 12.

The system in which the ROM is built into the single-chip microcomputer 1 has the advantage that since a mask ROM is used, the area occupied by the printed circuit board can be reduced, and costs can be reduced when the number of units is large. On the other hand, software changes, i.e. ROM
In the case of changing the instruction contents of 6, it is necessary to replace the single-chip microcomputer 1, which has the disadvantage that changing the software takes time and increases costs. There is a technique described below as a technique for improving this drawback.

FIG. 7 is a diagram illustrating control using an external ROM with a conventional single-chip microcomputer. In this figure, the external EPROM 7 and l"+01 are different from those in Figure 6.
There is an external ROM 2-2 consisting of 2. In this case, the internal ROM 6 of the single-chip microcontroller 1 can be used by itself, and the external ROM 6 of the external 1?
Switched to PROM 7. Furthermore, external [EPI?
The OM method usually has a structure in which the IC of the EPROM can be replaced, so it is easy to change the software, and it is easy to change the software. ff11
There is an advantage that the capability of a single deep microcomputer 1 can be expanded depending on the number of circuits, that is, devices and the purpose of use. That is, the problem with the software change shown in FIG. 6 is solved. On the other hand, the external EPROM method has the disadvantage that it occupies a large area on a printed circuit board and is more expensive than the case shown in FIG.

[Problems to be solved by the present invention]

however,! ! ! If it is obvious that the software will change to some extent at the time of manufacture, but it is not expected that the number of units that will have to change the software will be that large, use the external E as shown in Figure 7.
If the PROM method is adopted, there will be no particular problem for equipment that requires software changes, but even equipment that does not require software changes will be equipped with El'ROM and PIQ, which not only increases costs but also makes unnecessary changes. There is a problem in that printing requires a large area on one board.

With the built-in ROM system as shown in Figure 6, there is no particular problem for devices that do not change the software, but if you want to change the software, change the software! There is a problem in that the single chip in the lt position must be replaced.

Therefore, in view of the above problems, the present invention has developed an internal ROM and an external R
The purpose is to provide a switching device with OM.

[Means to solve the problem]

FIG. 1A is a diagram showing the use of an internal ROM, which is the principle configuration of the present invention, and FIG. 1B is a diagram showing the use of an external ROM, which is the principle configuration of the present invention. It is a figure showing OM switching. In the present invention, in order to solve the above problem, the internal ROM and external ROM switching device 2 is provided between the single-chip microcomputer 1 and the controlled circuit 3.

The internal ROM and external ROM switching device 2 consists of two connecting sections 5A and 5B, a jumper section 2-1, and an external ROM unit 2-2. Two connections 5A and 5B
is arranged between the bus line 4 that connects the single-chip microcomputer 1 and the controlled circuit 3. Jumper section 2-1
directly connects the two connecting portions 5A and 5B. The external ROM unit 2-2 is connected to the jumper section 2-1 and selectively to the two connection sections 5A and 5B, so that the internal ROM of the single-chip microcomputer 1 can be connected to the jumper section 2-1.
It can be switched from 6.

[For production]

In FIG. 1A, when the single-chip microcomputer 1 uses its internal ROM 6 to control the controlled circuit 3, the two connection parts 5A and 5B are directly connected, that is, short-circuited, by the jumper part 2-1.

In Figure 1B, the single-chip microcomputer 1
When controlling the controlled circuit 3 using the OM 7, the jumper section 2-1 in FIG. 1A is connected to the external ROM unit 22.
The purpose of soft modification can be achieved by replacing and connecting. Compared to the prior art shown in FIG. 6, two connecting portions 5A and 5B and a jumper portion 2-1 are additionally provided, but these can be made at low cost. Conventionally, when changing the software, it was necessary to replace the single-chip microcomputer, but such replacement is no longer necessary, and the software can be changed easily as shown in FIG. 1B. Especially when compared with the case where an external EPROM as shown in FIG. 7 is provided, the cost of the configuration shown in FIG. 1A is significantly lower.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2A is a diagram showing an internal ROM usage state according to an embodiment of the present invention, and FIG. 2B is a diagram showing an external ROM switching state according to an embodiment of the present invention. In these figures, the components different from those in FIGS. 6 and 7 are internal R.
This is an OM and external ROM switching unit 2, and its configuration will be explained below. The connecting portions 5A and 5B are comprised of sockets and are provided on the bus line 4 between the single-chip microcomputer 1 and the controlled circuit 3. The bus line 4 connected to the connection parts 5A and 5B consists of a total of 24 bits, for example, an 8-bit data line and 16-bit address line. Third
The figure is a diagram showing the connections in FIGS. 2A and 2B.

The connecting portion 5A is connected to the bus line 4 on the single-chip microcomputer 1 side, and the connecting portion 5B is connected to the bus line 4 on the controlled circuit side. Either the jumper section 2-1 or the external ROM unit 22 is set to the connecting sections 5A and 5B as shown in FIG. The jumper section 2-1 has a jumper wire 9 of the bus line 4 that directly connects or shorts the connecting sections 5A and 5B.

FIG. 4 illustrates the jumper section of FIG. 2A. In Figure 4 (
As shown in a), jumper wires 9 are connected to sockets 1-5A' and 5B' in jumper section 2-1, and sockets 5A' and 5B' are connected to respective socket sections of connection sections 5A and 5A. FIG. 4(b) shows another example, in which the jumper wire 9 is provided on the board.

The external ROM unit 2-2 shown in FIG. 2B is an external ROM.
7 and a parallel input/output ink face PIO12. FIG. 5 is a diagram illustrating the external ROM section of FIG. 2B. In FIG. 5(a), the external ROM unit 2-2
are connected by cables 13 to the respective connections 5A and 5B via sockets 5A' and 5B'. In Figure 5 (
b) shows an example in which the cable 13 is arranged on a board.

Next, the operation will be explained. When the jumper section 2-1 is attached to the connecting sections 5A and 5B, the terminal 8 is grounded and an L signal is generated at the terminal 8. This signal causes the internal ROM 6 of the single-chip microcomputer 1 to operate.

Subsequently, when the external ROM unit 2-2 is attached to the connection parts 5A and 5B in place of the jumper part 2-1, the terminal 8 becomes an oven, generates an H signal at the terminal 8, and this [■
The signal causes the operation of the internal ROM of the single-chip microcomputer 1 to be halted. Along with this, external ROM unit 2
-2's external ROM 7 is operated, and via PIO12,
A control signal is sent to the controlled circuit 3. Furthermore, it is also possible to switch from this state to the original jumper section 2-1.

〔Effect of the invention〕

As explained above, according to the present invention, a connection section, which is an inexpensive socket, is provided on the bus line between the controlled circuit and the single-chip microcomputer, and in normal control, the socket is short-circuited with an inexpensive jumper wire. In addition, an external ROM consisting of an external EPROM can be detachably attached to the socket according to the need for software changes, thereby reducing the cost of software changes.

[Brief explanation of the drawing]

FIG. 1A is a diagram showing the use of internal ROM, which is the principle configuration of the present invention. FIG. 1B is a diagram showing external ROM switching, which is the principle configuration of the present invention. FIG. 2A is a diagram showing the internal ROM, which is an embodiment of the present invention. FIG. 2B is a diagram showing the switching state of the external ROM section according to an embodiment of the present invention; FIG. 3 is a diagram showing the connections in FIGS. 2A and 2B; FIG. 4 is a diagram explaining the jumper section in FIG. 2A, FIG. 5 is a diagram explaining the external ROM section in FIG. 2B, and FIG. 6 is a diagram explaining control using a single-chip microcomputer using the conventional r<OM built-in method. Figure 7 shows a conventional external HPROM
FIG. 2 is a diagram illustrating control using a single-chip microcomputer according to the method. In the figure, 1... Single-chip microcomputer, 2... Internal ROM and external ROM switching device, 2-
DESCRIPTION OF SYMBOLS 1... Jumper part, 2-2... External ROM unit, 3... Controlled part, 5A, 5B... Connection part.

Claims (1)

[Claims] 1. A switching device between an internal ROM (6) and an external ROM (7) of a single-chip microcomputer (1) for a controlled circuit (3), comprising: There are two connections (5A
, 5B), and a removable jumper part (5A, 5B) that directly connects the two connection parts (5A, 5B) is provided between the two connection parts (5A, 5B).
2-1) and an external ROM unit (2-2) including the external ROM (7).