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order this document by AN1240/d semiconductor semiconductor semiconductor semiconductor motorola application note AN1240 ?mo torola inc., 1995 AN1240/d hc05 mcu software-driven async hr onous serial comm unication t ec hniques using the mc68hc705j1a by scott george csic mcu product engineering introduction this application note descr ibes a method f or asynchronous ser ial comm unication with a microcontroller unit (mcu) using standard input/output (i/o) por t pins and softw are which incor por ate noise and fr ame- error detection. if error detection is not needed, the code siz e ma y be reduced f or more ef?cient use of memory. overview a serial communication interf ace (sci) is a ser ial i/o sub system a vailable with many motorola mcus. this hardw are module pro vides full-duple x, univ ersal asynchronous receiv er/tr ansmitter-type (u ar t) ser ial comm unication betw een the mcu and other u art -type de vices , such as a cathode-r a y-tube (cr t) terminal, personal computer , or other mcus . the sci handles all tr ansmission and reception duties and b y so doing off-loads the cpu to perf or m other functions sim ultaneously . the sci is softw are programmable f or man y diff erent baud r ates . the receiv er can detect error conditions automatically , such as fr aming, noise, and overrun. some motorola mcus do not include an sci, speci?cally a lo w-cost, lo w-pin-count mcu such as the mc68hc705j1a. t o perf or m asynchronous ser ial comm unication, softw are m ust be used to em ulate an sci. in this case , the cpu w ould control i/o por t pins to perf or m the same functions as the receiv e data (rxd) and transmit data (txd) pins of a true hardware-driven sci. this applications software solution requirements are: ? speed optimization for maximum baud rate ? minimal code size ? easy con?guration for different baud rates ? ability to detect noise and framing errors while receiving. because the cpu is not as ef?cient as a dedicated hardware sci, software emulation has limitations: ? very fast baud rates are not attainable ? sci software consumes memory space and cpu bandwidth ? flexibility and features are reduced f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 2 if a particular application cannot be limited by these restrictions , then using an mcu with an sci w ould be appropriate. however, man y applications do not need the perf ormance or ?e xibility of an sci, and, in those cases, software emulation is a cost-effective solution. the abo v e requirements w ould be jeopardiz ed b y softw are em ulation of full-duple x tr ansmission. this software solution only operates in half-duplex mode. serial communication terminology and concepts sever al technical concepts and ter ms per taining to sci softw are oper ation are discussed here . note that message protocol is not discussed, since it is assumed the reader is kno wledgeab le about eff ectiv e sci communication. half-duplex operation in a half-duple x system, only one node tr ansmits at an y one time . the mcu cannot receiv e while it is tr ansmitting, and it cannot tr ansmit while it is receiving. this inability is in contr ast to the hardw are sci, which can tr ansmit and receiv e diff erent inf or mation at the same time . this is kno wn as a full-duple x system. transmission format the sci uses the standard non-retur n-to-zero (nrz) for mat consisting of one star t bit followed by one byte (eight bits) of data and one stop bit. this is commonly referred to as an 8-n-1 format (8 data bits, no parity bit, 1 stop bit). data is both tr ansmitted and receiv ed least signi?cant bit (lsb) ?rst. each bit has a dur ation, t p , which de?nes the baud rate. figure 1. nrz 8-n-1 transmission format as sho wn in figure 1, an idle line is high (logic one) pr ior to tr ansmission or reception, and the star t bit is low (logic z ero). each data bit is either high (logic one) or lo w (logic z ero). the stop bit is high (logic one). the start bit, eight data bits, and stop bit constitute one frame of data. noise detection on an asynchronous ser ial network, data transmitted b y one node ma y be received incorrectly by another node because of noise corr uption along the data path. t o minimiz e noise corr uption, the sci receiv er software routine samples each bit three times in the middle of each bit period (see figure 2). start bit stop bit 0 1 2 3 4 5 6 7 t p t p t p t p next start bit idle line t p = 1 bit period = 1/baud rate f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 3 figure 2. sci receiver sample points the true bit data is derived by the receiver by using a majority rule of the three samples. a noise condition occurs when the three samples are not identical. the sci receiv er softw are routine sets the half-carr y bit to signal a noise condition. frame error detection the stop bit is de?ned as a logic one. if the stop bit is received as a logic zero, a frame error has occurred. the sci receiver software routine uses the carry bit to signal a frame-error condition. application system overview the application of the sci softw are consists of an rs232-c ph ysical interf ace connecting an mcu to a dumb ter minal. as each char acter is typed on the ter minal s k e yboard, the ascii-equiv alent data is transmitted to the mcu. the mcu then transmits the ascii character back to the dumb terminal. if a noise or frame error occurs during the reception of the character, the appropriate leds are lit to signal the error. hardware description the motorola mc68hc705j1a mcu and the motorola mc145407 rs232-c tr ansmitter/receiver are used in this e xample (ref er to appendix a). the motorola mc34064 lo w-v oltage reset is connected to the reset pin to pro vide bro wn-out and slo w supply po w er-on protection. a r ibbon cab le connects the mc145407 to the dumb ter minal. a 4.0-mhz cr ystal oscillator cloc ks the mcu , and both the dumb ter minal and the sci receiver routine are con?gured for 9600 baud. other selectable baud rates also may be used. software description the sci software consists of tw o main subroutines to be called b y the main program. the receive routine, get_char , receiv es one b yte of data from the receiv e data pin (rxd) and places it into char , a v ariable in z ero-page ram. the get_char routine calls a subroutine , get_bit , which captures three samples of the state of rxd and adds them together to der iv e bit data and noise inf ormation. upon exiting get_char , the t s t p t s any data or stop bit t s = 8 cpu cycles t p = 1 bit period = 1/baud rate sampling points f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 4 carry bit is set if a noise condition occurred; otherwise, it is cleared. the half-carry bit is set if a frame error occurred; otherwise, it is cleared. char contains the received data. the transmit routine, put_char , transmits serially the contents of char using the transmit data pin (txd). both get_char and put_char call delay_13a , a subroutine which produces a dela y of 13*a cc + 12 cpu cycles, where acc is the value in the accumulator at the time the subroutine is called. see appendix b for ?owcharts and appendix c for the source code listing. the baud rate for both the receiver and transmitter is selected by changing baud_sel to 4, 8, 16, 32, 64, or 128 which, with a 4.0-mhz crystal oscillator, produces a baud r ate of 19.2 k, 9600, 4800, 2400, 1200 or 600 respectively. the baud rate for the receiver and the transmitter will be the same. appendix d speci?es receiver tolerances and transmitter accuracies for each baud rate. customization this section introduces possib le customization of the softw are sci concept. detailed descr iption of these ideas is beyond the scope of this application note. wake-up and time-out features wak e-up capability of the receiv er routine allo ws the cpu to e x ecute useful code while the rxd line is idle . both the rxd pin and the irq pin are connected to the rxd line . a negative tr ansition on the rxd line will cause an irq interrupt. the interrupt service routine can then call get_char . an excellent way to generate a negative transition on the rxd line is to transmit a zero ($00) immediately followed by the stream of data to be received. note that the zero is not received, but the data following the zero is received. time-out capability of the receiv er routine allo ws an interr upt to abor t an idle line condition. bef ore the get_char routine is called, the m ultifunction timer (mft) can be con?gured to interr upt after a time longer than the anticipated receiv e time . care should be tak en as to ho w the subroutine is entered and e xited. note that stack pointer housekeeping might be required. low voltage reset circuitry an mc34064 lo w-v oltage reset de vice has been included to sho w the most rob ust reset circuit. this pro vides protection from slo w-r amping po w er supplies . man y bench-type po w er supplies r amp slo wly, causing faulty power-on of mcus. the mc34064 holds the reset pin low until the power supply is within a speci?ed r ange . this also pro vides protection from bro wnout, when the mcus minim um v dd requirements are e xceeded. if such rob ust protection is not required, engineer ing judgment ma y be used to design a more cost-effective circuit. code minimization code size may be minimized b y eliminating code speci?c to noise detection if that f eature is not needed in an application. this could result in up to a 30% reduction of code space. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 5 conclusion sci receiv er and tr ansmitter softw are routines off er the application designer an alter nativ e to using a hardw are sci. the softw are routine listings contain the oper ational details . the routines ma y be used as listed or customized as determined by engineering requirements. an electronic listing of the source code in appendix c can be f ound on the motorola mcu bbs . the bbs phone n umber is (512) 891-3733. the ?le name is j1a_5407.arc and can be f ound on the csic bbs under the appnotes directory. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 6 appendix a f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 7 date: january 24, 1995 sheet 1 of 1 size document number rev a j1a_5407.sch 1 title hc705j1a bit banged sci to mc145407 motorola - csic strategic applications hc705j1a to mc145407 interface circuit c6 10uf c7 10uf c2- 3 vss 4 rx1 5 tx1 6 rx2 7 tx2 8 rx3 9 gnd 2 do3 12 c2+ 1 di2 13 di1 15 do1 16 vdd 17 c1- 18 vcc 19 c1+ 20 do2 14 tx3 10 di3 11 u2 mc145407p vdd c5 0.1uf c8 10uf c1 10uf 13 25 12 24 11 23 10 22 9 21 8 20 7 19 6 18 5 17 4 16 3 15 2 14 1 p2 female conn db25 gnd gnd gnd --> <-- gnd gnd d2 led vdd frame error d1 led vdd noise error gnd vdd osc1 1 osc2 2 reset 20 irq/vpp 19 pa0 18 pa1 17 pa2 16 pa3 15 pa4 14 pa5 13 pa6 12 pa7 11 pb0 8 vss 10 vdd 9 pb1 7 pb3 5 pb2 6 pb4 4 pb5 3 u1 mc68hc705j1ap c2 0.1uf <-- txd --> rxd y1 4.0mhz r1 390 r2 390 gnd c4 37pf gnd c3 37pf gnd 3 input 2 reset 1 u3 mc34064 vdd gnd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 8 appendix b turn off frame error led main frame error? call init call get_char noise? turn on frame error led call put_char turn off frame noise led turn on frame noise led yes no yes no f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 9 init acc = 0? return initialize txd and rxd pins initialize noise led initialize frame led return delay_13a wait 13 cpu cycles decrement acc put_char count = 9 clear carry txd pin = carry prepare for 1 bit delay call delay_13a count = 0? shift next data bit into carry decrement count call delay_13a return txd pin = 1 prepare for 1 bit delay no no yes yes f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 10 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 11 get_char false start? count = 8 noise reg = 0 call get_bit prepare for 1 bit delay shift data bit into char prepare for 1 bit delay decrement count noise? return xor noise data with char data set half-carry bit rxd idle? start bit begun? prepare for 1/2 bit delay call delay_13a call get_bit call delay_13a shift noise bit into noise reg count = 0? call get_bit noise? put frame bit into carry compute frame error bit call delay_13a yes yes yes yes yes yes no no no no no no f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 12 get_bit clear acc capture state of rxd oin return capture state of acc add to acc add to acc capture state of acc add to acc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 13 appendix c ***************************************************************************** ***************************************************************************** * * * main routine sci_01 - sci software transmit/receive routines * * * ***************************************************************************** * * * file name: sci_01.rtn copyright (c) motorola 1995 * * * * full functional description of routine design: * * program flow: * * reset: call init to initialize port pins * * call get_char to receive a byte of data * * light frame error led if frame error occurred * * light noise led if frame error occurred * * call put_char to transmit the received byte of data * * loop back to get_char call (endless loop) * * * ***************************************************************************** * * * part specific framework includes section * * * ***************************************************************************** #include 'h705j1a.frk' ; include the equates for the ; hc705j1a so all labels can ; be found. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 14 ***************************************************************************** * * * mor bytes definitions for the main routine * * * ***************************************************************************** org mor fcb $20 ****************************************************************************** * * * equates and ram storage * * * ****************************************************************************** *** i/o pin equates: serial_port equ $01 ; port used for serial port ; pins status_port equ $00 ; port used for driving led's. noise equ 4 ; pin # for noise led frame equ 5 ; pin # for frame led rxd equ 0 ; pin # for receive data pin txd equ 1 ; pin # for transmit data pin *** program constant equates: ; baud rate select table: baud_sel equ $08 ; baud_sel 4mhz osc 2mhz osc ; $04 19.2k 9600 ; $08 9600 4800 ; $10 4800 2400 ; $20 2400 1200 ; $40 1200 600 ; $80 600 300 *** ram variable allocation: org ram char rmb 1 ; data register for sci count rmb 1 ; temp storage variable f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 15 ***************************************************************************** * main - example program that continually echoes back received characters. * * * * input cond. - reset * * output cond. - none (infinite loop) * * stack used - 4 bytes * * variables used - none * * rom used - 28 bytes * ***************************************************************************** org rom ; start at the top of rom main rsp ; reset the stack pointer jsr init ; initialize port pins main_loop jsr get_char ; receive one byte of data ; from rxd pin bcc no_frame_error ; branch if no noise occured bclr frame,status_port ; turn on frame led bra continue ; don't check for noise -- ; it's undefined no_frame_err bset frame,status_port ; turn off frame led bhcs noise_error ; branch if noise occured bset noise,status_port ; turn off noise led bra continue ; skip next line of code yes_noise_err bclr noise,status_port ; turn on noise led continue jsr put_char ; transmit the received byte bra main_loop ; and prepare for next ; reception. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 16 ****************************************************************************** * init - initialize port pins for sci operation and for driving leds; * * called by main * * * * input cond. - none * * output cond. - txd = output initialize to 1, rxd = input, noise led = * * off, frame led = off. * * stack used - 0 bytes * * variables used - none * * rom used - 15 bytes * ****************************************************************************** init bset txd,serial_port ; init txd = 1 bset txd,serial_port+4 ; txd = output bclr rxd,serial_port+4 ; rxd = input bset noise,status_port ; noise led = off bset noise,status_port+4 ; noise = output bset frame,status_port ; frame led = off bset frame,status_port+4 ; frame = output rts ; exit (init) ****************************************************************************** * get_char - receive one byte of data from rxd pin; called by main * * * * input cond. - rxd pin defined as an input pin * * output cond. - char contains received data; x,acc undefined; * * half carry = 1 (frame occured) or 0 (no frame error); * * carry = 1 (noise and/or frame error occured) or 0 * * (no noise). * * stack used - 2 bytes * * variables used - char: storage for received data (1 byte) * * count: temporary storage (1 byte) * * rom used - 63 bytes * ****************************************************************************** f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 17 get_char lda #8 ;[2] receiving 8 data bits sta count ;[4] store value into ram clrx ;[3] used to store noise data get_start_bit brclr rxd,serial_port,* ;[5] wait until rxd=1 brset rxd,serial_port,* ;[5] wait for start bit lda #baud_sel-3 ;[2] prepare for 1/2 bit delay bsr delay_13a ;[13a+12] execute delay routine bsr get_bit ;[39] sample start bit lsra ;[3] noise bit -> carry; ; acc=filtered start bit bne get_start_bit ;[3] if false start, start over tsta ;[3] for timing purposes only tsta ;[3] for timing purposes only lda #2*(baud_sel-2) ;[2] prepare for 1 bit delay bsr delay_13a ;[13a+12] execute delay routine get_data_bits bsr get_bit ;[39] sample data bit rora ;[3] noise bit -> carry rorx ;[3] carry -> noise data reg rora ;[3] filtered data bit -> carry ror char ;[5] carry -> char lda #2*(baud_sel-3) ;[2] prepare for 1 bit delay bsr delay_13a ;[13a+12] execute delay routine tsta ;[3] for timing purposes only dec count ;[5] bit received, dec count bne get_data_bits ;[3] loop if more bits to get get_stop_bit bsr get_bit ;[39] sample stop bit lsra ;[3] noise bit -> carry ; acc=filtered stop bit sta count ;[4] store stop bit in count bcc yes_noise ;[3] if noise, then branch f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 18 txa ;[2] noise data -> acc eor char ;[3] xor noise with char, beq no_noise ;[3] and if result=0, ; then no noise in data ; reception yes_noise lda #$08 ;[2] set noise bit (half carry) add #$08 ;[2] by adding $8 to $8 no_noise lda count ;[3] retrieve stop data bit, coma ;[3] complement it, lsra ;[3] and shift it into carry ; for frame error bit rts ;[6] exit (get_char) ****************************************************************************** * get_bit - receive one bit of filtered data and noise info; called by * * get_char * * * * input cond. - rxd pin defined as an input pin * * output cond. - acc = 000000dn, where d = filtered data, n = noise info * * stack used - 0 bytes * * variables used - none * * rom used - 17 bytes * ****************************************************************************** get_bit clra ;[3] used to add sampled bits brset rxd,serial_port,samp_1 ;[5] sample 1st bit into carry samp_1 adc #0 ;[3] add it to acc brset rxd,serial_port,samp_2 ;[5] sample 2nd bit into carry samp_2 adc #0 ;[3] add it to acc brset rxd,serial_port,samp_3 ;[5] sample 3rd bit into carry samp_3 adc #0 ;[3] add it to acc rts ;[6] exit (get_bit) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 19 ***************************************************************************** * put_char - transmit data byte in char out onto txd pin; called by main * * * * input cond. - txd pin defined as an output pin and txd = 1; * * char contains byte to be tranmitted. * * output cond. - x,acc,char = undefined; * * stack used - 2 bytes * * variables used - char: storage for transmitted data (1 byte) * * rom used - 31 bytes (35 if sending two stop bits) * ***************************************************************************** put_char ldx #9 ;[2] be sending 8 data bits clc ;[2] clear carry for start bit put_data_bits bcc send_0 ;[3] if carry<>0, then bset txd,serial_port ;[5] send out a 1 bra jmp_bit ;[3] finished sending a 1 send_0 bclr txd,serial_port ;[5] else send a 0 bra jmp_bit ;[3] finished sending a 0 jmp_bit lda #2*(baud_sel-1)-1 ;[2] prepare for a 1 bit delay bsr delay_13a ;[13a+12] execute delay routine tsta ;[3] for timing purposes only ror char ;[5] get next data bit to send decx ;[3] one bit sent, so dec count bne put_data_bits ;[3] loop if more bits to send put_stop_bit nop ;[2] for timing purposes only bset txd,serial_port ;[5] send out a one lda #2*(baud_sel-1) ;[2] prepare for a 1 bit delay bsr delay_13a ;[13a+12] execute delay routine * add the next two lines to guarantee sending two stop bits: * lda #2*(baud_sel-1)+1 ;[2] prepare for a 1 bit delay * bsr delay_13a ;[13a+12] execute delay routine rts ;[6] exit (put_char) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola reser v es the r ight to mak e changes without fur ther notice to an y products herein. motorola mak es no w arranty , representation or guar antee regarding the suitability of its products f or any par ticular pur pose , nor does motorola assume an y liability ar ising out of the application or use of an y product or circuit, and speci?cally disclaims any and all liability , including without limitation consequential or incidental damages . "typical" parameters can and do vary in different applications. all operating parameters , including "t ypicals" m ust be v alidated f or each customer application b y customer's technical e xperts . motorola does not con vey an y license under its patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the f ailure of the motorola product could create a situation where personal injur y or death may occur . should buy er purchase or use motorola products f or an y such unintended or unauthor ized application, buy er shall indemnify and hold motorola and its of?cers, employees, subsidiaries, af?liates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injur y or death associated with such unintended or unauthor ized use, ev en if such claim alleges that motorola w as negligent regarding the design or manufacture of the part. motorola and are registered trademarks of motorola, inc. motorola, inc. is an equal opportunity/af?rmative action employer. literature distrib ution center s: usa: motorola liter ature distr ib ution; p .o . bo x 20912; phoenix, ar iz ona 85036. eur ope: motorola ltd.; european liter ature centre; 88 t anners dr ive , blak elands , milton k e ynes , mk14 5bp , england. jap an: nippon motorola ltd.; 4-32-1, nishi-gotanda, shinaga w a-ku, t oky o 141 j apan. asia-p a cific: motorola semiconductors h.k. ltd.; silicon harbour center , no .2 dai king street, t ai p o industr ial estate , t ai p o , n.t ., hong k ong. ****************************************************************************** * delay_13a - delay for 13*acc + 12 cycles; called by get_char and put_char * * * * input cond. - acc set to appropriate value (13*acc + 12 cycles) * * output cond. - acc = 0 * * stack used - 0 bytes * * variables used - none * * rom used - 7 bytes * ****************************************************************************** delay_13a nop ;[2] this is a 13-cycle loop nop ;[2] tsta ;[3] deca ;[3] decrement loop count bne delay_13a ;[3] loop if count not zero rts ;[6] exit (delay_13a) ****************************************************************************** * * * interrupt and reset vectors for main routine * * * ****************************************************************************** org reset fdb main f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
AN1240/d motorola 21 appendix d receiver tolerances the f ollo wing toler ances state the maxim um v ar iation of the a ver age bit per iod allo wab le f or accur ate reception of data without noise or frame error conditions occurring. transmitter accuracy the following table states the percent accuracy of the transmitted bit period to the ideal bit period. table 1 receiver tolerances baud rate for 4 mhz clock (bits/sec) baud rate for 2 mhz clock (bits/sec) bit period t p ( m s) bit period tolerance 19.2k n/a 52.08 +2.7%/-4.0% 9600 9600 104.2 +3.7%/-5.7% 4800 4800 208.3 +3.9%/-5.5% 2400 2400 416.7 +4.3%/-4.8% 1200 1200 833.3 +4.9%/-5.2% 600 600 1666.7 +4.9%/-5.4% n/a 300 3333.3 +4.9%/-5.1% table 2 transmitter accuracy baud rate for 4 mhz clock (bits/sec) baud rate for 2 mhz clock (bits/sec) ideal bit period t p ( m s) actual bit period t p ( m s) % accuracy 19.2k n/a 52.08 52.0 0.16% 9600 9600 104.2 104.0 0.16% 4800 4800 208.3 208.0 0.16% 2400 2400 416.7 416.0 0.16% 1200 1200 833.3 832.0 0.16% 600 600 1666.7 1664.0 0.16% n/a 300 3333.3 3328.0 0.16% f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/
motorola AN1240/d 22 references 1) motorola, m68hc11 reference manual , prentice hall, englewood cliffs, new jersey, 1989, order no. m68hc11rm/ad. 2) motorola, m68hc05 applications guide , revision 1, order no. m68hc05ag/ad. 3) motorola, mc68hc05j1a technical data , order no. m68hc05j1a/d 4) stev e leibson, the handbook of microcomputer interf acing, second edition , t ab books , inc., blue ridge summit, pennsylvania, 1989. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . www.datasheet.co.kr datasheet pdf - http://www..net/

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