diff options
Diffstat (limited to 'com.c')
| -rw-r--r-- | com.c | 259 |
1 files changed, 259 insertions, 0 deletions
@@ -0,0 +1,259 @@ +/**
+ * MPX OS
+ * CSI350 Operating Systems
+ * Fall 2013
+ * Averill Morash, Ben Burwell
+ * COM.C
+ */
+
+#include <dos.h>
+#include <stdio.h>
+#include <string.h>
+#include "mpx.h";
+
+
+void interrupt (*vect0c)();
+dcb com;
+
+int com_opened;
+
+int com_open(int * flag, int rate) {
+ unsigned char imr;
+ unsigned char mcr;
+ unsigned char ier;
+ unsigned char lcr;
+
+ disable();
+
+ if (com_opened == NULL || com_opened == 0) {
+ com_opened = 1;
+ } else {
+ return -2;
+ }
+
+ // modify the interrupt vector table
+ vect0c = getvect(0x0c);
+ setvect(0x0c, &com_int);
+
+ // set baud rate
+ // first we need to set bit 7 of LCR
+ // to be 1 so that we can set the baud
+ // rate divisor.
+ lcr = inportb(LCR);
+ lcr = lcr | 0x80;
+ outportb(LCR, lcr);
+
+ // Now we can access the divisor.
+ // Clock rate is 1.8432 MHz. We want
+ // 1200 bps/baud.
+ // 1843200 / (1200 * 16) = 96 = 0x0060
+ // So the MSB is 0x00 and the LSB is 0x60
+
+ if (rate != 1200) {
+ return -3;
+ }
+
+ outport(BRDR_MSB, 0x00);
+ outportb(BRDR_LSB, 0x60);
+
+ // Now set the LCR
+ lcr = inportb(LCR);
+
+ // b7, b3, b2 = 0
+ lcr = lcr & 0x73;
+
+ // b0, b1 = 1
+ lcr = lcr | 0x03;
+
+ outportb(LCR, lcr);
+
+ // set IMR to allow COM interrupts
+ // set b4 = 0
+ imr = inportb(IMR);
+ imr = imr & 0xef;
+ outportb(IMR, imr);
+
+ // set MCR to enable interrupts from
+ // the UART
+ // on MCR, b3 = 1
+ mcr = inportb(MCR);
+ mcr = mcr | 0x08;
+ outportb(MCR, mcr);
+
+ // use IER to indicate which serial
+ // interrupts are enabled
+ // b0 = 1, b1 = 0
+ ier = inportb(IER);
+ ier = ier | 0x01;
+ ier = ier & 0xfd;
+ outportb(IER, ier);
+
+ // set up the DCB
+ com.event_flag = flag;
+ dcb_init(&com);
+
+ // enable interrupts
+ enable();
+
+ return 0;
+}
+
+void com_close() {
+ disable();
+ setvect(0x0c, vect0c);
+ enable();
+}
+
+void interrupt com_int() {
+ int iir;
+ int ret = 0; //0 indicates not finished, 1 indicated finshed
+
+ // check IIR to see what caused the interrupt
+ iir = inportb(IIR);
+ // only look at bits 1, 2
+ iir = iir & 0x06; // 0000-0110
+
+ if (iir == 0x02) { // 0000-0010
+ ret = com_write_int();
+ } else if (iir == 0x04) { // 0000-0100
+ ret = com_read_int();
+ } else {
+ // something is wrong
+ return;
+ }
+
+ if (ret == 1) {
+ IO_complete();
+ }
+
+ // write end of interrupt to 8259
+ outportb(0x20, 0x20);
+
+ return;
+
+}
+
+int com_read(char far * buffer, int far * length) {
+
+ char dq;
+ int i;
+
+ if (&com == NULL) {
+ // com not yet open
+ return -1;
+ }
+
+ // check for invalid length
+ if (*length < 1) {
+ return -3;
+ }
+
+ // check if DCB is free
+ if (com.current_op != NO_OP) {
+ // previous IO not yet complete
+ // TODO: we should block this process
+ return -2;
+ }
+
+ com.buffer = buffer;
+ com.length = length;
+ com.current_op = READ_OP;
+ com.count = 0;
+
+ strcpy(buffer, "");
+
+ i = 0;
+
+ while (com.ring_count > 0 && strlen(buffer) < *length) {
+
+ dq = dcb_dequeue(&com);
+ //strcat(buffer, &dq);
+ buffer[i] = dq;
+ i++;
+ }
+
+ buffer[i] = '\0';
+ com.count = i;
+
+ return 0;
+}
+
+int com_write(char far * buffer, int far * length) {
+ int ier;
+
+ // check that com has been initialized
+ if (&com == NULL) {
+ return -1;
+ }
+
+ // check that com is not busy
+ if (com.current_op != NO_OP) {
+ return -2;
+ }
+
+ // check that the length is valid
+ if (*length < 1) {
+ return -3;
+ }
+
+ // initialize DCB
+ com.buffer = buffer;
+ com.length = length;
+ com.current_op = WRITE_OP;
+ com.count = 0;
+
+ // enable THR interrupts
+ ier = inportb(IER);
+ // bit 1 should be 1
+ ier = ier | 0x02;
+ outportb(IER, ier);
+
+ return 0;
+}
+
+int com_read_int() {
+ char rbr;
+
+ rbr = inportb(RBR);
+
+ if (com.current_op == READ_OP && com.count < *(com.length)) {
+ if (rbr == 0x0d || com.count == (*(com.length) - 1)) {
+ com.buffer[com.count] = '\0';
+ com.count++;
+ *com.length = com.count;
+ com.current_op = NO_OP;
+ *(com.event_flag) = 1;
+ return 1;
+ } else {
+ com.buffer[com.count] = rbr;
+ com.count++;
+ }
+ } else {
+ dcb_enqueue(&com, rbr);
+ }
+
+ return 0;
+}
+
+int com_write_int() {
+ int ier;
+
+ // if there are more characters to write
+ if (*(com.length) > com.count) {
+ // write a character
+ outportb(THR, com.buffer[com.count]);
+ com.count++;
+ return 0;
+ } else {
+ // no chars to write
+ // disable THR interrupts
+ ier = inportb(IER);
+ ier = ier & 0xfd;
+ outportb(IER, ier);
+
+ // set event flag
+ com.current_op = NO_OP;
+ *(com.event_flag) = 1;
+ return 1;
+ }
+}
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