Important: This application note demonstrates how to connect the MAX6901 to an 8051 microcontroller and provides basic interface program routines. The microcontroller used in this article is DS2250, and the software is written in C language.
MAX6901 pin configuration
Overview This application note demonstrates the connection between the MAX6901 and the 8051 microcontroller, and provides basic interface program routines. The microcontroller used in this article is DS2250, and the software is written in C language. Working principle The program uses three general-purpose port pins of the microcontroller to control the 3-wire bus. The microcontroller sends a command / address byte to the MAX6901 to start data transmission. Subsequently, the microcontroller sends other bytes to the MAX6901 or provides SCLK, according to the command byte to send or receive data.
The circuit schematic is shown in Figure 1, and the software is shown in Figure 2.
Figure 1. Schematic of daughter card "(PDF download)
Figure 2. Code list / ******************************************** ******************************* / / * DEMO6901.c * / / ********** ************************************************** *************** / / * #pragma code symbols debug * / #include / * Prototypes for I / O funcTIons * / #include / * Register declaraTIons for DS5000 * / / ** *************************** Defines ********************** ********** / sbit CE = P0 ^ 0; sbit SCLK = P0 ^ 1; sbit IO = P0 ^ 2; / ***************** ****** FuncTIon Prototypes ************************** / void writebyte (); void iniTIalize (); void disp_clk_regs (); void burstramread (); void burstramwrt (); / ************************* Global Variables ************ *************** / uchar cy, yr, mn, dt, dy, hr, min, sec, msec; void reset_3w () / * ---- reset the 3-wire interface ---- * / {SCLK = 0; CE = 0; IO = 0; / * program IO pin to 0V * /} void wbyte_3w (uchar W_Byte) / * --- write one byte to the DUT --- * / {uchar i; CE = 1; for (i = 0; i <8; ++ i) {if (W_Byte & 0x01) IO = 1; / * set port pin high to read data * / else IO = 0; SCLK = 0; SCLK = 1; W_Byte >> = 1;}} uchar rbyte_3w () / * --- read one byte from the DUT --- * / {uchar i ; uchar R_Byte = 0; CE = 1; IO = 1; for (i = 0; i <8; ++ i) {SCLK = 1; SCLK = 0; if (IO) {R_Byte >> = 1; R_Byte + = 0x80;} else R_Byte >> = 1;} return R_Byte;} void writebyte () / * ----- write one byte, prompt for address and data ------ * / {uchar add; uchar dat ; / * Get Address & Data * / printf ("Enter the Write Address (h) ADDRESS (80,82,84 ...):"); scanf ("% bx", & add); printf ("DATA (0 -ff): "); scanf ("% bx ", & dat); reset_3w (); wbyte_3w (add); wbyte_3w (dat); reset_3w ();} void initialize () / * ----- init clock data using user entries ----- * / / * Note: NO error checking is done on the user entries! * / {reset_3w (); wbyte_3w (0x0f); / * control register write address * / wbyte_3w (0x00); / * clear write protect * / reset_3w (); printf ("Enter the year (0-99):"); scanf ("% bx", & yr); printf ("Enter the month (1-12):"); scanf ("% bx", & mn); printf ("Enter the date (1-31): "); scanf ("% bx ", & dt); printf (" Enter the day (1-7): "); scanf ("% bx ", & dy); printf (" Enter the hour (1-23): "); scanf ("% bx ", & hr); hr = hr & 0x3f; / * force clock to 24 hour mode * / printf (" Enter the minute (0-59): "); scanf ("% bx " , & min); printf ("Enter the second (0-59):"); scanf ("% bx", & sec); reset_3w (); wbyte_3w (0xbe); / * clock burst write * / wbyte_3w (sec); wbyte_3w (min); wbyte_3w (hr); wbyte_3w (dt); wbyte_3w (mn); wbyte_3w (dy); wbyte_3w (yr); wbyte_3w (0); / * control * / reset_3w (); wbyte_3w (0x92); wbyte_3w (0x20); / * century data * / reset_3w ();} void disp_clk_regs () / * --- loop reading clock, display when secs change --- * / {uchar mil, pm, prv_sec = 99; while (! RI) / * Read & Display Clock Registers * / {reset_3w (); wbyte_3w (0xbf); / * clock burst read * / sec = rbyte_3w (); min = rbyte_3w (); hr = rbyte_3w (); dt = rbyte_3w ( ); mn = rbyte_3w (); dy = rbyte_3w (); yr = rbyte_3w (); cy = rbyte_3w (); / * dummy read of control register * / reset_3w (); wbyte_3w (0x93); / * century byte read address * / cy = rbyte_3w (); reset_3w (); if (hr & 0x80) mil = 0; else mil = 1; if (sec! = prv_sec) / * display every time seconds change * / {if (mil) {printf ("% 02bX % 02bX /% 02bX /% 02bX% 01bX ", cy, yr, mn, dt, dy); printf ("% 02bX:% 02bX:% 02bX ", hr, min, sec);} else {if (hr & 0x20) pm = 'P'; else pm = 'A'; hr & = 0x1f; / * strip mode and am / pm bits * / printf ("% 02bx% 02bx /% 02bx /% 02bx% 02bx", cy, yr, (mn & 0x1f), dt, dy); printf ("% 02bx:% 02bx:% 02bx% cM", hr, min, sec, pm);}} prv_sec = sec;} RI = 0; / * Swallow keypress to exit loop * /} void burstramread () / * ------ read RAM using burst mode ----- * / {uchar k; printf ("MAX6901 RAM contents:"); reset_3w (); wbyte_3w (0xff); / * ram burst read * / for (k = 0; k <31; k ++) {if (! (k% 8)) printf (""); printf ("% 02.bX", rbyte_3w ());} reset_3w ();} void burstramwrt (uchar Data) / * ------ write RAM using burst mode ------- * / {uchar j, k; reset_3w (); wbyte_3w ( 0xfe); / * ram burst write * / for (k = 0; k <31; ++ k) {wbyte_3w (Data);} reset_3w ();} main (void) / * ------ ----------------------------------------------- * / { uchar i, M, M1; while (1) {printf ("MAX6901 build% s", __DATE__); printf ("CI Clock Init"); printf ("CR Clock Read CW Clock Write"); printf ("RR Read RAM RW RAM Write "); printf (" Enter Menu Selection: "); M = _getkey (); switch (M) {case 'C': case 'c': printf (" Enter Clock Routine to run: C ") ; M1 = _getkey (); switch (M1) {case 'I': case 'i': initialize (); break; case 'R': case 'r': disp_clk_regs (); break; case 'W': case 'w': writebyte (); break;} break; case 'R': case 'r': printf ("Enter Ram Routine to run: R"); M1 = _getkey (); switch (M1) {case 'R ': case' r ': burstramread (); break; case' W ': case' w ': printf ("Enter the data to write:"); scanf ("% bx", & i); burstramwrt (i); break;} break;}}}
MAX6901 pin configuration
Overview This application note demonstrates the connection between the MAX6901 and the 8051 microcontroller, and provides basic interface program routines. The microcontroller used in this article is DS2250, and the software is written in C language. Working principle The program uses three general-purpose port pins of the microcontroller to control the 3-wire bus. The microcontroller sends a command / address byte to the MAX6901 to start data transmission. Subsequently, the microcontroller sends other bytes to the MAX6901 or provides SCLK, according to the command byte to send or receive data. The circuit schematic is shown in Figure 1, and the software is shown in Figure 2.
Figure 1. Schematic of daughter card "(PDF download)
Figure 2. Code list / ******************************************** ******************************* / / * DEMO6901.c * / / ********** ************************************************** *************** / / * #pragma code symbols debug * / #include / * Prototypes for I / O funcTIons * / #include / * Register declaraTIons for DS5000 * / / ** *************************** Defines ********************** ********** / sbit CE = P0 ^ 0; sbit SCLK = P0 ^ 1; sbit IO = P0 ^ 2; / ***************** ****** FuncTIon Prototypes ************************** / void writebyte (); void iniTIalize (); void disp_clk_regs (); void burstramread (); void burstramwrt (); / ************************* Global Variables ************ *************** / uchar cy, yr, mn, dt, dy, hr, min, sec, msec; void reset_3w () / * ---- reset the 3-wire interface ---- * / {SCLK = 0; CE = 0; IO = 0; / * program IO pin to 0V * /} void wbyte_3w (uchar W_Byte) / * --- write one byte to the DUT --- * / {uchar i; CE = 1; for (i = 0; i <8; ++ i) {if (W_Byte & 0x01) IO = 1; / * set port pin high to read data * / else IO = 0; SCLK = 0; SCLK = 1; W_Byte >> = 1;}} uchar rbyte_3w () / * --- read one byte from the DUT --- * / {uchar i ; uchar R_Byte = 0; CE = 1; IO = 1; for (i = 0; i <8; ++ i) {SCLK = 1; SCLK = 0; if (IO) {R_Byte >> = 1; R_Byte + = 0x80;} else R_Byte >> = 1;} return R_Byte;} void writebyte () / * ----- write one byte, prompt for address and data ------ * / {uchar add; uchar dat ; / * Get Address & Data * / printf ("Enter the Write Address (h) ADDRESS (80,82,84 ...):"); scanf ("% bx", & add); printf ("DATA (0 -ff): "); scanf ("% bx ", & dat); reset_3w (); wbyte_3w (add); wbyte_3w (dat); reset_3w ();} void initialize () / * ----- init clock data using user entries ----- * / / * Note: NO error checking is done on the user entries! * / {reset_3w (); wbyte_3w (0x0f); / * control register write address * / wbyte_3w (0x00); / * clear write protect * / reset_3w (); printf ("Enter the year (0-99):"); scanf ("% bx", & yr); printf ("Enter the month (1-12):"); scanf ("% bx", & mn); printf ("Enter the date (1-31): "); scanf ("% bx ", & dt); printf (" Enter the day (1-7): "); scanf ("% bx ", & dy); printf (" Enter the hour (1-23): "); scanf ("% bx ", & hr); hr = hr & 0x3f; / * force clock to 24 hour mode * / printf (" Enter the minute (0-59): "); scanf ("% bx " , & min); printf ("Enter the second (0-59):"); scanf ("% bx", & sec); reset_3w (); wbyte_3w (0xbe); / * clock burst write * / wbyte_3w (sec); wbyte_3w (min); wbyte_3w (hr); wbyte_3w (dt); wbyte_3w (mn); wbyte_3w (dy); wbyte_3w (yr); wbyte_3w (0); / * control * / reset_3w (); wbyte_3w (0x92); wbyte_3w (0x20); / * century data * / reset_3w ();} void disp_clk_regs () / * --- loop reading clock, display when secs change --- * / {uchar mil, pm, prv_sec = 99; while (! RI) / * Read & Display Clock Registers * / {reset_3w (); wbyte_3w (0xbf); / * clock burst read * / sec = rbyte_3w (); min = rbyte_3w (); hr = rbyte_3w (); dt = rbyte_3w ( ); mn = rbyte_3w (); dy = rbyte_3w (); yr = rbyte_3w (); cy = rbyte_3w (); / * dummy read of control register * / reset_3w (); wbyte_3w (0x93); / * century byte read address * / cy = rbyte_3w (); reset_3w (); if (hr & 0x80) mil = 0; else mil = 1; if (sec! = prv_sec) / * display every time seconds change * / {if (mil) {printf ("% 02bX % 02bX /% 02bX /% 02bX% 01bX ", cy, yr, mn, dt, dy); printf ("% 02bX:% 02bX:% 02bX ", hr, min, sec);} else {if (hr & 0x20) pm = 'P'; else pm = 'A'; hr & = 0x1f; / * strip mode and am / pm bits * / printf ("% 02bx% 02bx /% 02bx /% 02bx% 02bx", cy, yr, (mn & 0x1f), dt, dy); printf ("% 02bx:% 02bx:% 02bx% cM", hr, min, sec, pm);}} prv_sec = sec;} RI = 0; / * Swallow keypress to exit loop * /} void burstramread () / * ------ read RAM using burst mode ----- * / {uchar k; printf ("MAX6901 RAM contents:"); reset_3w (); wbyte_3w (0xff); / * ram burst read * / for (k = 0; k <31; k ++) {if (! (k% 8)) printf (""); printf ("% 02.bX", rbyte_3w ());} reset_3w ();} void burstramwrt (uchar Data) / * ------ write RAM using burst mode ------- * / {uchar j, k; reset_3w (); wbyte_3w ( 0xfe); / * ram burst write * / for (k = 0; k <31; ++ k) {wbyte_3w (Data);} reset_3w ();} main (void) / * ------ ----------------------------------------------- * / { uchar i, M, M1; while (1) {printf ("MAX6901 build% s", __DATE__); printf ("CI Clock Init"); printf ("CR Clock Read CW Clock Write"); printf ("RR Read RAM RW RAM Write "); printf (" Enter Menu Selection: "); M = _getkey (); switch (M) {case 'C': case 'c': printf (" Enter Clock Routine to run: C ") ; M1 = _getkey (); switch (M1) {case 'I': case 'i': initialize (); break; case 'R': case 'r': disp_clk_regs (); break; case 'W': case 'w': writebyte (); break;} break; case 'R': case 'r': printf ("Enter Ram Routine to run: R"); M1 = _getkey (); switch (M1) {case 'R ': case' r ': burstramread (); break; case' W ': case' w ': printf ("Enter the data to write:"); scanf ("% bx", & i); burstramwrt (i); break;} break;}}}
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