link_cable.h

#ifndef _LINK_CABLE_H_
#define _LINK_CABLE_H_
 
#include "config.h"
 
#if (MODULE_LINK_CABLE != 0)
 
#include "types.h"

 
// Input/output direction for SEGA MD console port 2 (set individually for each bit)
// Determines the data line operation mode (input or output) and controls the interrupt request mask from external devices.
// Essentially, this is memory address 0xA1000B for data transfer control
// via SEGA Link Cable (CTRL port register CTRL 2 in SEGA documentation)
// Bit 7 (INT) - Interrupt on SYN line signal. 0 = disabled; 1 = enabled.
// Bit 6 (PC6) - Data line "SYN" mode. 0 = input; 1 = output.
// Bits 0-5 (PC0-PC5) - Data line mode. 0 = input; 1 = output.
#define LCP_Ctrl                                (*(vu8*) 0xa1000b)
 
// State of port 2 on SEGA MD console
// Essentially, this is memory address 0xA10005 for direct data transfer
// via SEGA Link Cable (DATA register of CTRL port 2 in SEGA documentation)
//
// Lower 4 bits (0-3) are used for data transfer.
//
// Bit addressing features between consoles:
// Bit 5 in the current console corresponds to bit 6 in the other console
// for the same memory address 0xA10005. If we change bit 5 on our console,
// bit 6 will change in the other console's LCP_Data variable, and vice versa -
// if bit 5 is changed on the other console, bit 6 will change on our console.
//
// Bits 0-3 at address 0xA10005 will have the same value in both consoles,
// i.e., if we change these bits on one console, they will also change on the other.
// Which console is currently responsible for this is determined by the LCP_Ctrl state -
// i.e., which data line is in output mode (sending data),
// and which is in input mode (receiving data).
#define LCP_Data                                (*(vu8*) 0xa10005)
 
// Bit 5 is set to 1, others to 0. Primarily used to set bit 5 to 1
// in LCP_Data and LCP_Ctrl to signal the other console that it can
// read or send data via Link Cable.
#define LCP_BIT5                                0b00100000
 
// Bit 6 is set to 1, others to 0. Mainly used to determine
// whether bit 6 is set in LCP_Data, signaling that
// data can be read from the other console or sent to the other console via Link Cable.
#define LCP_BIT6                                0b01000000
 
// Bits 7 and 5 are set to 1, other bits are 0. Used to set these bits in LCP_Ctrl, which indicates
// readiness for data exchange through console port 2 upon external interrupt EX-INT (External Interrupt
// in SEGA documentation), i.e., reading data from the port (data reception) in the external interrupt handler LCP_slaveCycle().
//
// LCP_Ctrl bit values:
// - Interrupt on SYN line signal enabled, bit 7 = 1
// - Data line PC5 in output mode (transmission), bit 5 = 1
// - Data lines PC6, PC4, PC3, PC2, PC1, PC0 in input mode (reception). Corresponding bits = 0
//
// At the "hardware" level for my code this means:
// - Enable pins 0-3 of controller port 2 for data reception
// - Pin 5 signals that data has been received by our console (on the other console this will be bit 6 in LCP_Data)
// - Pin 6 signals that data has been sent by the other console (the other console should change bit 5 in its LCP_Data)
#define LCP_BIT7_AND_BIT5               0b10100000;
 
// Bits 5, 3, 2, 1, 0 are set to 1, others are 0. Used to set these bits in LCP_Ctrl, which means
// starting the data write cycle to port 2 (data transmission) by triggering an external interrupt on the slave console.
//
// I.e., on the master console, the LCP_masterCycle() method should be called from the main game code, which will set
// the bits in LCP_Ctrl to the state specified above, and on the slave console we will previously trigger an external
// interrupt that will halt the main game code execution and call the LCP_slave() method. This will occur when on the
// master console the 5th bit in LCP_Data is reset to 0 in the LCP_startSendCycle() method.
//
// LCP_Ctrl bit values:
// - Interrupt on SYN line signal disabled, bit 7 = 0
// - Data lines PC5, PC3, PC2, PC1, PC0 in output mode (transmission), bits 5, 3, 2, 1, 0 = 1
// - Data lines PC6, PC4 in input mode (reception). Corresponding bits = 0
//
// At the "hardware" level for my code this means:
// - Enable pins 0-3 of controller port 2 for data transmission
// - Pin 5 signals that data can be read by the other console (on the other console this will be bit 6 in LCP_Data)
// - Pin 6 signals that data has been read by the other console (the other console should change bit 5 in its LCP_Data)
#define LCP_BIT_5_3_2_1_0               0b00101111;
 
// Mask 00001111. Mainly used to reset the high 4 bits in a byte to 0
#define LCP_LO_BITS                     0b00001111
 
// Mask 11110000. Mainly used to reset the low 4 bits in a byte to 0
#define LCP_HI_BITS                     0b11110000
 
// Timeout - used for waiting for data from the other console (waiting for reset or set of bit 6 in LCP_Data)
#define LCP_TIME_OUT                    0x40
 
// Maximum packet size for data transmission via Link Cable
#define LCP_PACKET_SIZE                 2048
 

 

void LCP_open();
 

void LCP_init();
 

void LCP_close();
 

void LCP_objectToPacketForSend(u8 *transferObject, u16 objectType , u16 *objectTypeSizes);
 

u16 LCP_getNextObjectFromReceivePacket(u8 *transferObject, u16 *objectSizes);
 

void LCP_masterCycle();
 

u16 LCP_getError();
 
#endif // MODULE_LINK_CABLE
 
#endif // _LINK_CABLE_H