/*-------------------------------------------

send.c
contains code that will send data to a board
that contains the receive.c code

data flow is as follows:
send port			receive port
data (0..3)	<-->	data (0..3)
ack_img(4)	-->		ack_img(4)
ack_ram(5)	-->		ack_ram(5)
req_img(6)	<--		req_img(6)
req_ram(7)	<--		req_ram(7)

--------------------------------------------*/

#include <90s8515.h>
#include <delay.h>

#define SEND_PORT	PORTB
#define SEND_PIN	PINB
#define SEND_DIR	DDRB   

#define ACK_IMG		SEND_PORT.4
#define ACK_RAM		SEND_PORT.5

#define REQ_IMG		SEND_PIN.6
#define REQ_RAM		SEND_PIN.7

#define AND_MASK	0x0f

#define TRUE        1
#define FALSE       0

#define	STORE		0
#define RETRIEVE		1

unsigned char sector[512];
unsigned char mode=STORE;
unsigned int loc=0;

// send_init() MUST be called before send is ever called
void send_init(){
	SEND_PORT = 0x00;		// clear the send port, no pull-ups
	SEND_DIR = 0x30;		// control pins are output
	
	delay_ms(100);			// delay for other board to turn on
}

void send_img_nibble(unsigned char data){
	// output the data
	SEND_PORT = data & AND_MASK;
	
	ACK_IMG = TRUE;				// acknowledge the request
	while(REQ_IMG == TRUE){}	// wait for the other board to grab data

	ACK_IMG = FALSE;			// drop the ack
}

void send_ram_nibble(unsigned char data){
	// output the data
	SEND_PORT = data & AND_MASK;
	
	ACK_RAM = TRUE;				// acknowledge the request
	while(REQ_RAM == TRUE){}	// wait for the other board to grab data

	ACK_RAM = FALSE;			// drop the ack	
}

unsigned char get_ram_nibble(){
	// get the data
	unsigned char ret;
	ret = SEND_PIN & AND_MASK;

	ACK_RAM = TRUE;				// acknowledge the receipt
	while(REQ_RAM == TRUE){}	// wait for other board to drop req

	ACK_RAM = FALSE;			// drop the ack

	return ret;
}

void ram_check(){
	if(REQ_RAM == TRUE){
		if(mode == STORE){
			PORTD.4=0;
			sector[loc] = (get_ram_nibble() << 4) & 0xf0;
			while(REQ_RAM == FALSE){}
			sector[loc] = sector[loc] | (get_ram_nibble() & 0x0f);
			loc++;
			if(loc == 512){
				mode = RETRIEVE;
				loc = 0;
			}
		} else {
			PORTD.4=1;
			SEND_DIR = 0x3f;
			send_ram_nibble(sector[loc] >> 4);
			while(REQ_RAM == FALSE){}
			send_ram_nibble(sector[loc]);
			SEND_DIR = 0x30;             
			loc++;
			if(loc == 512){
				mode = STORE;
				loc = 0;
			}
		}
	}
}

void send(unsigned char data){
	while(REQ_IMG == FALSE){
		ram_check();
	}

	SEND_DIR = 0x3f;
	send_img_nibble(data >> 4);
	while(REQ_IMG == FALSE){}
	send_img_nibble(data);
	SEND_DIR = 0x30;
}