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sci.c File Reference

Detailed Description

Provides SCI (Serial Communications Interface) routines for BeeOS.

Based on information provided in S12SCIV3.pdf by Motorola, Inc. v03.02.

See also:
../include/sci.h

Definition in file sci.c.

#include "../include/beeos.h"
#include "../include/asm/ports.h"
#include "../include/asm/ports_std.h"
#include "../include/arch/param.h"
#include "../include/sci.h"

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Defines

#define IN_SCI

Functions

void sci0_init (ushort baud)
void sci_tx (unsigned char *sci_base, char data)
char sci_rx (unsigned char *sci_base, char data)
 TX a byte of data; wait for in-progress transmission to finish first.

Define Documentation

#define IN_SCI
 

Definition at line 31 of file sci.c.

Function Documentation

void sci0_init (  ushort  baud  ) 
 

Definition at line 35 of file sci.c.

References ASM_MOVW_MM, CPU_CLOCK, DDRS, PERS, PPSS, SCI0BDH, SCI0CR1, SCI0CR2, SCI0DRH, SCI0SR1, SCI0SR2, SCI_IREN, SCI_RE, SCI_TE, SCI_TNP0, SCI_TNP1, TOUSHORT, and ushort. 

00036     {
00041         ushort t = (ushort) ( ((long int)(CPU_CLOCK / 10L / 16L)) / (long int) baud);
00042         
00043         ASM_MOVW_MM(t, SCI0BDH);
00044         /* IREN, TNP[1:0] should be zero as long as baud is not an illegal value, */
00045         SCI0BDH = SCI0BDH &~SCI_IREN &~SCI_TNP1 &~SCI_TNP0; /* but clear anyway */
00046         SCI0CR1 = 0x00; /* No parity, 8bits data */
00047         SCI0CR2 = 0x00 | SCI_RE | SCI_TE;   /* Enable TX & RX */
00048         if (SCI0SR1) SCI0DRH = 0x00;    /* Clear TDRE: read from SCIDR */
00049         TOUSHORT(SCI0DRH) = 0x00;                   /* and write to it */
00050         SCI0SR2 = 0x00; /* BRK char = 10/13bits, Single wire mode = TX in, etc */
00051         DDRS |= 0x03;   /* DDR, etc. are overridden when SCI is enabled, but */
00052         PERS |= 0X03;   /* if WOMS is set, need internal pullups (overridden */
00053         PPSS &= ~0x03;  /* if WOMS isn't set). */
00054         
00055         return;
00056     }

char sci_rx (  unsigned char *  sci_base,
char  data
) 
 

TX a byte of data; wait for in-progress transmission to finish first.

Parameters:
sci_base The base addr. for the SCI's registers
Return values:
data The RX'd byte
This is a nasty time-wasting polling function. Use interrupts instead. This function assumes 8 bit data.

Definition at line 128 of file sci.c.

References SCI_RDRF, SCIDRL, and SCISR1. 

00129     {   
00137         while (!(sci_base[SCISR1] & SCI_RDRF));
00138         
00139         return (char) sci_base[SCIDRL];
00140     }

void sci_tx (  unsigned char *  sci_base,
char  data
) 
 

Definition at line 95 of file sci.c.

References __asm__(), SCI_TDRE, SCIDRL, and SCISR1.

Referenced by putchar(). 

00096     {   
00104     /* Why oh why... while (!(sci_base[SCISR1] & SCI_TDRE)); does not work. After 2
00105      * hours on the simulator, reading compiler ASM output, stepping, tracing...
00106      * GCC simply will not produce code that reads from SR1 properly.
00107      * Hence the asm.
00108      */
00109         /*
00110             while (!(sci_base[SCISR1] & SCI_TDRE)); ;;tx_flush()
00111             sci_base[SCIDRL] = data;
00112         */
00113         __asm__ __volatile__ ( 
00114             "sci_tx_hack:\
00115             \n\tldaa %1         ;; SCI_TDRE bit\
00116             \n\tanda %0         ;; AND w/SCISR1\
00117             \n\tbeq sci_tx_hack ;; If bit is zero, keep looping\
00118             \n\tmovb %3, %2     ;; Write next byte into TX shift register"
00119             :                                               /* Output */
00120             : "m" (sci_base[SCISR1]), "n" (SCI_TDRE),       /* Input */
00121                 "m" (sci_base[SCIDRL]), "m" (data)
00122             : "%a", "%ccr"                                  /* Clobbered */
00123         );
00124         
00125         return;
00126     }

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