Memory control device, mobile terminal, and computer-readable recording medium
A memory control device of the present invention comprises a determination section ( 34 ) for determining whether a time point of start of a writing operation falls within a risky period; and a delay control section ( 32 ) for delaying, in a case where the determination section ( 34 ) determines that the time point of the start of the writing operation falls within the risky period, a time point of the start of one of the writing operation and the reading operation which one is higher in operation rate, said one of the writing operation and the reading operation being delayed by a predetermined delay period.
1. A memory control device which conducts (i) a writing operation in which data transferred from a host is written in a frame memory and (ii) a reading operation in which the data is read out from the frame memory so as to transfer the data to a display,
the memory control device comprising:
a Liquid Crystal Display (LCD) controller connected to the frame memory; wherein
the LCD controller determines, in a case where a readout period from start of the reading operation to end of the reading operation is different in length from a writing period from start of the writing operation to end of the writing operation, whether start of the writing operation falls within a risky period which is predetermined based at least on a difference between the readout period and the writing period;
the LCD controller delays, in a case where the LCD controller determines that the start of the writing operation falls within the risky period, the start of one of the reading operation and the writing operation which one is higher in operation rate, said one of the reading operation and the writing operation being delayed by a predetermined delay period which is predetermined based on a difference between the readout period and the writing period;
in a case where the reading operation is higher in operation rate than the writing operation, the risky period is set as a time period from (i) a time point preceding the end of the reading operation by a length of the writing period to (ii) the start of the reading operation; and
in a case where the writing operation is higher in operation rate than the reading operation, the risky period is set as a time period from (i) the start of the reading operation to (ii) the time point preceding the end of the reading operation by the length of the writing period.
2. The memory control device as set forth in claim 1 , wherein
the LCD controller delays, in a case where it is determined that the start of the writing operation falls within the risky period, the start of the reading operation by suspending, by the delay period, a line counter for generating a line address used in transferring the data to the display.
3. The memory control device as set forth in claim 1 , wherein
the LCD controller delays, in a case where it is determined that the start of the writing operation falls within the risky period, the start of the writing operation by delaying transmission and reception of permission information in response to request information in a sequence control until the start of the writing operation no longer falls within the risky period, the sequence control being a control in which transfer of the data from the host to the frame memory is started upon completion of transmission and reception of the request information and the permission information between the host and the display, the request information being indicative of a request to start the writing operation, the permission information being in response to the request information and indicative of permission to start the writing operation.
4. The memory control device as set forth in claim 3 , wherein
the LCD controller further determines whether the start of the reading operation falls within a time period from (i) the transmission and reception of the permission information in response to the request information between the host and the display to (ii) start of transfer of the data from the host to the frame memory, and
in a case where the LCD controller determines that the start of the reading operation falls within a time period from (i) a time point of completion of the transmission and reception of the permission information in response to the request information between the host and the display to (ii) the start of transfer of the data from the host to the frame memory, the LCD controller suspends a line counter to generate a line address used in transferring the data to the display.
5. The memory control device as set forth in claim 2 , wherein when the LCD controller receives, during the risky period, information which is always transferred before the writing operation of the data, LCD controller determines that the start of the writing operation of the data falls within the risky period.
6. The memory control device as set forth in claim 1 , wherein
the LCD controller adjusts a length of a front porch period of each frame period in the reading operation of the data,
the LCD controller determines whether or not the start of the writing operation falls within a time period from end of the risky period to end of the reading operation of data in a previous frame,
in a case where the LCD controller determines that the start of the writing operation falls within the period from the end of the risky period to the end of the reading operation of the data in a previous frame, the LCD controller advancing the start of the reading operation of the data by causing the length of the front porch period to be equal to or shorter than a length of a front porch period in the previous frame, and
in a case where the LCD controller does not determine that the start of the writing operation falls within the period from the end of the risky period to the end of the reading operation of data in the frame previous to the data, the LCD controller causing the length of the front porch period to be equal to or longer than the length of the front porch period in the previous frame.
7. The memory control device as set forth in claim 1 , wherein
the LCD controller determines whether or not the start of the writing operation falls within a time period from end of the risky period to the end of the reading operation, and
in a case where the LCD controller determines that the start of the writing operation falls within the period from the end of the risky period to the end of the reading operation, the LCD controller delays the start of the reading operation by the delay period.
8. The memory control device as set forth in claim 2 , wherein
in the case where the reading operation is higher in operation rate than the writing operation,
the risky period is set as a time period from (i) a time point preceding the end of the reading operation by a length of the writing period to (ii) start of a vertical sync signal, and
the LCD controller delays the start of the writing operation so that a time period which is a sum of a vertical front porch period and a vertical sync signal pulse period for the writing operation is longer than a time period which is a sum of a vertical front porch period and a vertical sync signal pulse period for the reading operation.
9. The memory control device as set forth in claim 2 , wherein
in the case where the reading operation is higher in operation rate than the writing operation,
the risky period is set as a time period from (i) a time point preceding the end of the reading operation by a length of the writing period to (ii) start of a vertical sync signal, and
transfer of the data from the host to the frame memory is started, upon completion of transmission and reception of request information and permission information between the host and the display, the request information being indicative of a request to start the writing operation, the permission information being in response to the request information and indicative of permission to start the writing operation.
10. The memory control device as set forth in claim 3 , wherein
in the case where the writing operation is higher in operation rate than the reading operation,
the risky period is set as a time period from (i) start of a vertical sync signal to (ii) a time point preceding the end of the reading operation by a length of the writing period, and
transfer of the data from the host to the frame memory is started, upon completion of transmission and reception of request information and permission information between the host and the display, the request information being indicative of a request to start the writing operation, the permission information being in response to the request information and indicative of permission to start the writing operation.
11. A mobile terminal, comprising a memory control device as set forth in claim 1 .
12. A non-transitory computer-readable recording medium, in which a memory control program for causing a computer to function as a memory control device as set forth in claim 1 is recorded, the memory control program causing the computer to function as the LCD controller of the memory control device.