LCD Commands
| Code | Description | Execution time** | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| RS | R/W | DB7 | DB6 | DB5 | DB4 | DB3 | DB2 | DB1 | DB0 | |||
| Clear display | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | Clears display and returns cursor to the home position (address 0). | 1.64mS |
| Cursor home | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | * | Returns cursor to home position (address 0). Also returns display being shifted to the original position. DDRAM contents remains unchanged. | 1.64mS |
| Entry mode set | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | I/D | S | Sets cursor move direction (I/D), specifies to shift the display (S). These operations are performed during data read/write. | 40uS |
| Display On/Off control | 0 | 0 | 0 | 0 | 0 | 0 | 1 | D | C | B | Sets On/Off of all display (D), cursor On/Off (C) and blink of cursor position character (B). | 40uS |
| Cursor/display shift | 0 | 0 | 0 | 0 | 0 | 1 | S/C | R/L | * | * | Sets cursor-move or display-shift (S/C), shift direction (R/L). DDRAM contents remains unchanged. | 40uS |
| Function set | 0 | 0 | 0 | 0 | 1 | DL | N | F | * | * | Sets interface data length (DL), number of display line (N) and character font(F). | 40uS |
| Set CGRAM address | 0 | 0 | 0 | 1 | CGRAM address | Sets the CGRAM address. CGRAM data is sent or received after this setting. | 40uS | |||||
| Set DDRAM address | 0 | 0 | 1 | DDRAM address | Sets the DDRAM address. DDRAM data is sent or received after this setting. | 40uS | ||||||
| Read busy-flag and address counter | 0 | 1 | BF | DDRAM address | Reads Busy-flag (BF) indicating internal operation is being performed and reads address counter contents. | 0uS | ||||||
| Write to CGRAM or DDRAM | 1 | 0 | write data | Writes data to CGRAM or DDRAM. | 40uS | |||||||
| Read from CGRAM or DDRAM | 1 | 1 | read data | Reads data from CGRAM or DDRAM. | 40uS | |||||||
Notes:
- DDRAM = Display Data RAM.
- CGRAM = Character Generator RAM.
- DDRAM address corresponds to cursor position.
- Address Counter is used for both DDRAM and CGRAM.
- * = Don't care.
- ** = Based on Fosc = 250KHz.
In this video, you will know how to clear RAM cache and increase your RAM virtually#clearcache#boostRAM#clearramcache. 1048576 bytes total contiguous extended memory 0 bytes available contiguous extended memory 941056 bytes available XMS memory MS-DOS resident in High Memory Area mem /f. Display the amount of conventional memory free. When using the mem /c command from a DOS window in Windows, no upper blocks are seen, as shown in the above example.
| Bit | Settings | |
|---|---|---|
| I/D | 0 = Decrement cursor position | 1 = Increment cursor position |
| S | 0 = No display shift | 1 = Display shift |
| D | 0 = Display off | 1 = Display on |
| C | 0 = Cursor off | 1 = Cursor on |
| B | 0 = Cursor blink off | 1 = Cursor blink on |
| S/C | 0 = Move cursor | 1 = Shift display |
| R/L | 0 = Shift left | 1 = Shift right |
| DL | 0 = 4-bit interface | 1 = 8-bit interface |
| N | 0 = 1/8 or 1/11 Duty (1 line) | 1 = 1/16 Duty (2 lines) |
| F | 0 = 5x7 dots | 1 = 5x10 dots |
| BF | 0 = Can accept instruction | 1 = Internal operation in progress |
Clear Display
Details
Writes space code (20h) into all DD RAM addresses. Sets address counter to DD RAM location 0. Returns display to its original state if it was shifted. In other words, the display disappears and the cursor or blink goes to the left edge of the display (the first line if 2 lines are displayed). Sets entry mode I/D to 1 (Increment Mode). Entry mode shift (S) bit remains unchanged.
Cursor Home
Returns the cursor to the home position (Address 0). Returns display to its original state if it was shifted.
Details
Sets the address counter to DD RAM location 0 in the address counter. Returns display to its original state if it was shifted. DD RAM contents remain unchanged. The cursor or blink goes to the left edge of the display (the first line if 2 lines are displayed).
Entry Mode Set
Sets the effect of subsequent DD RAM read or write operations. Sets the cursor move direction and specifies or not to shift the display. These operations are performed during data read and write.
Details
Specifies whether to increment (I/D = 1) or decrement (I/D = 0) the address counter after subsequent DD RAM read or write operations.
If S = 1 the display will be shifted to the left (if I/D = 1) or right (if I/D = 0) on subsequent DD RAM write operations. This makes it looks as if the cursor stands still and the display moves when each character is written to the DD RAM. if S = 0 the display will not shift on subsequent DD RAM write operations.
Display ON/OFF
Controls display of characters and cursor.
How To Clear Ram Cache
Details
D: The display is ON when D = 1 and OFF when D = 0. The DD RAM contents remain unchanged.
C: The cursor is displayed when C = 1 and is not displayed when C = 0.
The cursor is displayed as 5 dots in the 8th line when the 5 x 7 dot character font is selected and as 5 dots in the 11th line when the 5 x 10 dot character font is selected.
B: The character at the the cursor position blinks when B = 1.
Drivers vertex standard. Blinking is performed by switching between all blank dots and the display character every 409.6 ms.
Cursor and Display Shift
Details
Shifts cursor position or display to the right or left without writing or reading display data. This function is used to correct or search for the display. In a 2-line display, the cursor moves to the 2nd line when it passes the 40th digit of the 1st line. Notice that the 1st and 2nd line displays will shift at the same time. When the displayed data is shifted repeatedly each line only moves horizontally. The 2nd line of the display does not shift into the 1st line position.
Function Set
Details
This command should be issued only after automatic power-on initialization has occurred, or as part of the module initialization sequence.
DL: Sets interface data length
- Data sent or received in 8 bit lengths (DB7-DB0) when DL = 1
Data sent or received in 4 bit lengths (DB7-DB4) when DL = 0
When the 4 bit length is selected, data must be sent or received in pairs of 4-bits each. The most-significant 4 bits are sent or received first.
F: Sets character font
Note that a 1 line x 16 character display is treated as a 2 line x 8 character display. The first `line' is the left eight character positions on the display and the second `line' is the right eight character positions. This also means that the 16 characters on the display do not occupy 16 sequential DD RAM locations.
Set CG RAM Address
Sets the CG RAM address. Subsequent read or write operations refer to the CG RAM.
Details
Sets the specified value (AAAAAA) into the address counter. Subsequent read or write operations transfer data from, or to, the character generator RAM.
Cmd Command Clear Ram
Set DDRAM Address
Sets the DD RAM address. Subsequent read or writes refer to the DD RAM.
Details
Sets the specified value (AAAAAAA) into the address counter. Subsequent read or write operations transfer data from, or to, the display RAM. Note: Adjacent display RAM locations do not necessarily refer to adjacent display positions.
Read busy flag and address counter
Reads the state of the busy flag (BF) and the contents of the address counter.
Details
Reads the busy flag (BF) that indicates the state of the LCD module. BF = 1 indicates that the module is busy processing the previous command. BF = 0 indicates that the module is ready to perform another command.
The value of the address counter is also returned. The same address counter is used for both CG and DD RAM transfers.
This command can be issued at any time. It is the only command which the LCD module will accept while a previous command is still being processed.
Write data to CG or DD RAM
Navalny twitter. Details
Writes a byte (DDDDDDDD) to the CG or the DD RAM. The destination (CG RAM or DD RAM) is determined by the most recent `Set RAM Address' command. The location to which the byte will be written is the current value of the address counter. After the byte is written the address counter is automatically incremented or decremented according to the entry mode. The entry mode also determines whether or not the display will shift. Github readme file example pdf.
Read data from CG or DD RAM
Details
Reads a byte (DDDDDDDD) from the CG or DD RAM. The source (CG RAM or DD RAM) is determined by the most recent `Set RAM Address' command. The location from which the byte will be read is the current value of the address counter. After the byte is reda the address counter is automatically incremented or decremented according to the entry mode.
The mem command allows users to determine how much memory is used and how much is available.
TipWindows Vista, 7, 8, or 10 users should use the Windows utility to determine how much RAM is installed and available. See: How to find how much RAM is installed on a computer.
Availability
The mem command is an external command that is available for the following Microsoft operating systems as mem.exe.
Mem syntax
Displays the amount of used and free memory in your system.
| /CLASSIFY or /C | Classifies programs by memory usage. Lists the size of programs, provides a summary of memory in use, and lists the largest memory block available. |
| /DEBUG or /D | Displays the status of all modules in memory, internal drivers, and other information. |
| /FREE or /F | Displays information about the amount of free memory left in both conventional and upper memory. |
| /MODULE or /M | Displays a detailed listing of a module's memory use. This option must be followed by the name of a module, optionally separated from /M by a colon. |
| /PAGE or /P | Pauses after each screen full of information. |
Mem examples
This command would display information about your memory, as seen in the examples below.
Microsoft Windows 95 and Windows 98 example output:
Windows 2000 and Windows XP example output:
Display the amount of conventional memory free.
Mem issues
Cmd Clear Laptop Ram
When using the mem /c command from a DOS window in Windows, no upper blocks are seen, as shown in the above example. In Windows 0 bytes are shown because Windows reserves all global upper memory blocks for Windows.
MS-DOS 6.2 and above does not accept or recognize more than 64 MB of ram when typing mem.
Additional information
Cmd Clear Ram Cache
- See our memory definition for further information and related links on this term.