JPH038016A - Latch data bit operating circuit - Google Patents

Abstract

PURPOSE:To improve efficiency in a software by providing first and second select circuits to select whether the respective bits of latch data are maintained as they are, converted to new values or 0 or 1 is made effective as the new value of the bit. CONSTITUTION:The most significant bit of the latch data is defined as D7 and bit data written by a CPU in a select circuit 2a is defined as input D7. Effective bit data select inputs SL0 and SL1 are applied to set whether the input D7 is made effective when the value of the bit is 0, made effective when the value is 1 or made always effective. The output of the circuit 2a is the output of a gate in a block. Then, when the bit data of preceding time are remained as they are, 0 is outputted and when the bit data are newly written, 1 is outputted. A select circuit 1a is a select circuit to output either the bit data of the preceding time or the newly written bit data to a latcher 3a. For a control signal to be the selection, the output of the circuit 2a is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the manipulation of latch data of an output port, and more particularly to a latch data bit manipulation circuit.

[Conventional technology]

Conventionally, when changing arbitrary bits of the latch data of an output port using software, the data written to that port was stored in the software (reserved in the RAM area) in order to avoid affecting other bits. ), and when manipulating a certain bit of latch data, refer to the previous data and change only the necessary bits, then write the changed output data to the output port and store the value again (R
We are taking a method to secure it in the AM area).

[Problem to be solved by the invention]

In the conventional method described above, it is necessary to set a RAM area to store output data for each output port, and each time latch data is written by software, data information is pulled out from the RAM area, referenced, and changed. After that, RA again
An operation is required to store it in the M area. Therefore, it has the disadvantage that it is inefficient in terms of software and cannot respond to cases where high-speed changes are required.

[Means to solve the problem]

The latch data bit manipulation circuit of the present invention includes a first select circuit that selects whether to leave each bit of latch data output to an output port as it is or change it to a new value, and a first select circuit that selects whether to leave each bit of latch data output to an output port as it is or change it to a new value, and a new bit value of 0. and a second select circuit that selects whether to enable 1 or 1.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the same figure, the latch data bit manipulation circuit includes a select circuit 2 that outputs a control signal for selecting whether to validate each bit value of the latch data of the previous output port or to validate a new bit value. , and a select circuit 1 which receives the above control signal and selects the previous bit data or newly written data to be input to the latch 3.

FIG. 2 is a specific circuit diagram using the most significant bit (D7) of data as an example. Bit data input D7 written by the CPU in the select circuit 2a and valid bit data select inputs SLO and SLI that set whether to enable it when it is O, enable it when it is 1, or always enable it.
There is. The output of the select circuit 2a is the gate output within the block, and when the previous bit data is left as is, it becomes ``0''.
``'', 1'' is output when newly written bit data is written.

The select circuit 1a is a select circuit that outputs either the previous bit data or the newly written bit data to the latch 3a, and the output of the select circuit 2a is used as the control signal for selection.

Although FIG. 2 is an example of only bit 7, if the data is 8 bits, similar connections may be made.

〔Effect of the invention〕

As explained above, in the present invention, when software changes only an arbitrary bit of latch data output from a certain port, the software operation is minimized so as not to affect other bits, and the capacity of the software is reduced. It has the effect of reducing and increasing efficiency.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram. 1.2...Select circuit, 3...Latcher.

Claims (1)

[Claims] A first select circuit that selects whether to leave each bit of the latch data output to the output port as is or change it to a new value, and enable 0 or 1 as the new bit value. A latch data bit manipulation circuit comprising: a second select circuit for selecting one of the latch data bits;