"1602 adopts standard 14 pin interface, in which:
Pin 1: VSS is the ground power supply
Pin 2: VDD connected to 5V positive power supply
Pin 3: V0 is the contrast adjustment terminal of LCD. The contrast is the weakest when connected to the positive power supply and the highest when connected to the grounding power supply. If the contrast is too high, a "ghost" will be generated. When in use, the contrast can be adjusted through a 10k potentiometer
Pin 4: RS is register selection, data register is selected at high level and instruction register is selected at low level.
Pin 5: RW is a read-write signal line. Read at high level and write at low level. When RS and RW are at low level together, instructions or display addresses can be written; when RS is at low level, RW is at high level, busy signals can be read; when RS is at high level, RW is at low level, data can be written.
Pin 6: terminal e is the enable terminal. When terminal e jumps from high level to low level, the LCD module executes the command.
Pins 7 ~ 14: d0 ~ D7 are 8-bit bidirectional data lines.
In addition, pins "a" and "K" are backlight pins, "a" is positive and "K" is negative, which will illuminate the backlight.
The character generation memory (cgrom) inside the 1602 LCD module has stored 160 different dot matrix character graphics, as shown in Table 1. These characters include Arabic numerals, case of English letters, common symbols, Japanese Kanas, etc. each character has a fixed code, such as the code of uppercase English letter "a" is 01000001b (41h), When displaying, the module displays the dot matrix character graphics in address 41h, and we can see the letter "a"
The controller inside the 1602 LCD module has 11 control commands, as shown in Table 2,
Its read-write operation, screen and cursor operation are realized through instruction programming（ Note: 1 is high level, 0 is low level)
Instruction 1: clear the display, the instruction code is 01h, and the cursor is reset to the address 00h position
Instruction 2: reset the cursor and return the cursor to address 00h
Instruction 3: cursor and display mode setting I / D: cursor moving direction, high level moving right, low level moving left s: whether all words on the screen move left or right. High level means valid, low level means invalid
Command 4: display switch control. D: Control the on and off of the overall display. High level means on display and low level means off display. C: control the on and off of the cursor. High level means with cursor and low level means without cursor. B: control whether the cursor flashes, high level flashes and low level does not flash
Instruction 5: cursor or display shift s / C: move the displayed text at high level and move the cursor at low level
Instruction 6: function setting command DL: 4-bit bus at high level and 8-bit bus at low level n: single line display at low level, double line display at high level F: 5x7 dot matrix characters at low level and 5x10 dot matrix characters at high level
Instruction 7: character generator RAM address setting
Instruction 8: DDRAM address setting
Instruction 9: read busy signal and cursor address BF: it is the busy flag bit. High level indicates busy. At this time, the module cannot receive commands or data. If low level indicates not busy.
Instruction 10: write data
Instruction 11: read data
The LCD module is a slow display device, so before executing each instruction, be sure to confirm that the busy flag of the module is low, indicating that it is not busy, otherwise the instruction will be invalid. To display characters, first enter the display character address, that is, tell the module where to display characters. Table 3 is the internal display address of dm-162.
For example, if the address of the first character in the second line is 40H, can the cursor be positioned at the position of the first character in the second line by directly writing 40H? This does not work because the highest bit D7 is required to be constant as high level 1 when writing the display address, so the actually written data should be 01000000B (40H) + 10000000B (80h) = 110000000b (C0H)
RSEQUP3.7
RWEQUP3.6
EEQUP3.5
movp3，#0ffh
MOVP1，#01H; Clear screen
ACALLENABLE
MOVP1，#38H; 8-bit lattice
ACALLENABLE
MOVP1，#0FH; On display
ACALLENABLE
MOVP1，#06H; Move Cursor
ACALLENABLE
MOVP1，#80H; Display location
ACALLENABLE
l3:movp1，#01h
acallenable
movdptr，#table1; Send the first sentence
callwrite1
callenable
MOVP1，#0C0H; Write display start address (first position on the second line)
ACALLENABLE; Call write command subroutine
callwrite1
callenable
movp1，#01h
calldelay1
calldelay1
calldelay1
jmpl3
ENABLE：; Send command
CLRRS
CLRRW
CLRE
ACALLDELAY
SETBE
RET
write1：; Send string
movr1，#00h
a1:mova，r1
movca，@a+dptr
callwrite2
incr1
cjnea，#00h，a1; Use 00h as string end flag
ret
write2：; Send single character
movp1，a
setbrs
clrrw
clre
calldelay
setbe
ret
delay：; Delay subroutine
movr7，#255
d1:movr6，#255
d2:djnzr6，d2
djnzr7，d1
ret
delay1：
movr7，#255
delay2:movr6，#255
djnzr6，$
djnzr7，delay2
ret
; Each table below is a sentence, with 00h as the end of each sentence.
table1:db20h，20h，20h，57h，45h，4ch，43h，4fh，4dh，45h，20h，54h，4fh，20h，20h，20h，20h，00h
table2:db20h，57h，57h，57h，2Eh，4dh，43h，55h，39h，39h，2Eh，43h，4Fh，4Dh，20h，20h，20h，00h
End, read the full text, technology zone
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