ST7920 - Topwaydisplay.com

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ST7920Serial interface :ST7920 is in serial interface mode when pull down PSB pin. Two pins (SCLK and SID) are used to complete the data transfer.Only write data is available.When connecting several ST7920, chip select(CS)must be used. Only when(CS)is high the serial clock(SCLK)can beaccepted. On the other hand, when chip select(CS)is low ST7920 serial counter and data will be reset. Transmission will beterminated and data will be cleared. Serial transfer counter is set to the first bit. For a minimal system with only one ST7920 andone MPU, only SCLK and SID pins are necessary. CS pin should pull to high.ST7920’s serial clock(SCLK)is asynchronous to the internal clock and is generated by MPU. When multiple instruction/data istransferred instruction execution time must be considered. Must wait for the previous instruction to finish before sending thenext. ST7920 has no internal instruction buffer area.When starting a transmission a start byte is required. It consists of 5 consecutive 〝1〞(sync character). Serial transfer counterwill be reset and synchronized. Following 2 bits for read/write(RW)and register/data select(RS). Last 4 bits is filled by 〝0〞。After receiving the sync character and RW and RS bits, every 8 bits instruction/data will be separated into 2 groups. Higher4 bits(DB7~DB4)will be placed in first section followed by 4 〝0〞. And lower 4 bits(DB3~DB0)will be placed in secondsection followed by 4 〝0〞.CSSCLK1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24SID1 1 1 1 1 RW RS 0 D7 D6 D5 D4 0 0 0 0 D3 D2 D1 D0 0 0 0 0SynchronizingBit stringHigherdataLowerdata1 st byte 2 nd byteTiming Diagram of Serial Mode Data TransferV3.1 26/42 2003/04/11
ST79208051 demo program for serial interface;--------------------------------------------------------------; Write data from A into INSTRUCTION Register;--------------------------------------------------------------WRINS:SETB CSSETB SID ; SID = 1CLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.7 ; SID = A.7SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.6 ; SID = A.6SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.5 ; SID = A.5SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.4 ; SID = A.4SETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.3 ; SID = A.3SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.2 ; SID = A.2SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.1 ; SID = A.1SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.0 ; SID = A.0SETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKCLR CSCALL DLY8RET;-------------------------------------------------; Write data from A into DATA Register;-------------------------------------------------WRDATA:SETB CSSETB SID ; SID = 1CLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SID ; SID = 1SETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.7 ; SID = A.7SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.6 ; SID = A.6SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.5 ; SID = A.5SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.4 ; SID = A.4SETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.3 ; SID = A.3SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.2 ; SID = A.2SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.1 ; SID = A.1SETB SCLK ; READ DATA FROM SIDCLR SCLKMOVBIT SID, A.0 ; SID = A.0SETB SCLK ; READ DATA FROM SIDCLR SCLKCLR SID ; SID = 0SETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKSETB SCLK ; READ DATA FROM SIDCLR SCLKCLR CSCALL DLY8RETV3.1 27/42 2003/04/11
Page 2 and 3: ST7920ST7920 Specification Revision
Page 5 and 6: ST7920Pin coordinatesNo. Name X Y1
Page 7 and 8: ST7920Pin DescriptionName No. I/O C
Page 9 and 10: ST7920Voltage doublerVssreference v
Page 11 and 12: ST7920Display data RAM(DDRAM)There
Page 13 and 14: ST7920DDRAM data(char. code)B B BB1
Page 15 and 16: ST7920GDRAM Vertical address(Y)0123
Page 17 and 18: ST7920Instruction set 2: (RE=1: ext
Page 19 and 20: ST7920Description of basic instruct
Page 21 and 22: ST7920• FUNCTION SETRS RW DB7 DB6
Page 23 and 24: ST7920Description of extended instr
Page 28 and 29: ST79208 bit interface:POWER ONWait
Page 30 and 31: ST7920Built in voltage boosterVoutV
Page 32 and 33: ST7920Absolute Maximum RatingsChara
Page 34 and 35: ST7920AC Characteristics (T A = 25
Page 36 and 37: ST79208 bit interface timing diagra
Page 38 and 39: ST7920Serial interface timing diagr
Page 40 and 41: ST7920V3.1 40/42 2003/04/11Applicat
Page 42: ST7920Application circuit 3:LCD: 2L

ST7920 - Topwaydisplay.com

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