--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jcart.c	Tue Dec 25 11:12:26 2018 -0800
@@ -0,0 +1,87 @@
+#include "genesis.h"
+
+static io_port *get_ports(m68k_context *m68k)
+{
+	genesis_context *gen = m68k->system;
+	if (!gen->extra) {
+		io_port *ports = calloc(2, sizeof(io_port));
+		ports[0].device_type = IO_GAMEPAD3;
+		ports[0].device.pad.gamepad_num = 3;
+		ports[1].device_type = IO_GAMEPAD3;
+		ports[1].device.pad.gamepad_num = 4;
+		io_control_write(ports, 0x40, 0);
+		io_control_write(ports + 1, 0x40, 0);
+		gen->extra = ports;
+	}
+		
+	return gen->extra;
+}
+
+void *jcart_write_w(uint32_t address, void *context, uint16_t value)
+{
+	m68k_context *m68k= context;
+	io_port *ports = get_ports(m68k);
+	value = value << 6 & 0x40;
+	io_data_write(ports, value, m68k->current_cycle);
+	io_data_write(ports + 1, value, m68k->current_cycle);
+	return context;
+}
+
+void *jcart_write_b(uint32_t address, void *context, uint8_t value)
+{
+	if (address & 1) {
+		return jcart_write_w(address, context, value);
+	}
+	return context;
+}
+
+uint16_t jcart_read_w(uint32_t address, void *context)
+{
+	m68k_context *m68k= context;
+	io_port *ports = get_ports(m68k);
+	//according to Eke, bit 14 is forced low, at least on the Micro Machines 2 cart
+	//TODO: Test behavior of actual cart
+	uint16_t value = io_data_read(ports, m68k->current_cycle) << 8;
+	value |= io_data_read(ports + 1, m68k->current_cycle);
+	return value;
+}
+
+uint8_t jcart_read_b(uint32_t address, void *context)
+{
+	m68k_context *m68k= context;
+	io_port *ports = get_ports(m68k);
+	return io_data_read(ports + (address & 1), m68k->current_cycle);
+}
+
+void jcart_adjust_cycles(genesis_context *context, uint32_t deduction)
+{
+	io_port *ports = get_ports(context->m68k);
+	io_adjust_cycles(ports, context->m68k->current_cycle, deduction);
+	io_adjust_cycles(ports + 1, context->m68k->current_cycle, deduction);
+}
+
+void jcart_gamepad_down(genesis_context *context, uint8_t gamepad_num, uint8_t button)
+{
+	io_port *ports = get_ports(context->m68k);
+	if (gamepad_num == ports[1].device.pad.gamepad_num) {
+		ports++;
+	} else if (gamepad_num != ports[0].device.pad.gamepad_num) {
+		ports = NULL;
+	}
+	if (ports) {
+		io_port_gamepad_down(ports, button);
+	}
+}
+
+void jcart_gamepad_up(genesis_context *context, uint8_t gamepad_num, uint8_t button)
+{
+	io_port *ports = get_ports(context->m68k);
+	if (gamepad_num == ports[1].device.pad.gamepad_num) {
+		ports++;
+	} else if (gamepad_num != ports[0].device.pad.gamepad_num) {
+		ports = NULL;
+	}
+	if (ports) {
+		io_port_gamepad_up(ports, button);
+	}
+}
\ No newline at end of file