After making some more analog outputs so I could see what's happening with gran trak 10:



Code
NETLIST_ANALOG_OUTPUT(config, "maincpu:data0", 0).set_params("DATA0", "bmp", FUNC(bitmap_printer_device::update_data0));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data1", 0).set_params("DATA1", "bmp", FUNC(bitmap_printer_device::update_data1));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data2", 0).set_params("DATA2", "bmp", FUNC(bitmap_printer_device::update_data2));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data3", 0).set_params("DATA3", "bmp", FUNC(bitmap_printer_device::update_data3));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data4", 0).set_params("DATA4", "bmp", FUNC(bitmap_printer_device::update_data4));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data5", 0).set_params("DATA5", "bmp", FUNC(bitmap_printer_device::update_data5));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data6", 0).set_params("DATA6", "bmp", FUNC(bitmap_printer_device::update_data6));
NETLIST_ANALOG_OUTPUT(config, "maincpu:data7", 0).set_params("DATA7", "bmp", FUNC(bitmap_printer_device::update_data7));

#define DEBUGNLAO(x,y) NETLIST_ANALOG_OUTPUT(config, "maincpu:"#x, 0).set_params(#y, "bmp", FUNC(bitmap_printer_device::update_##x));

DEBUGNLAO(a0,A0)
...
and then a corresponding printing routine:

Code
#define DEBUGITEM(x) NETDEV_ANALOG_CALLBACK_MEMBER(update_##x) {printf("UPDATE " #x ": %f  "#x"= %f\n",time.as_double(),data); }

DEBUGITEM(data0)
DEBUGITEM(data1)
DEBUGITEM(data2)
DEBUGITEM(data3)
DEBUGITEM(data4)
DEBUGITEM(data5)
DEBUGITEM(data6)
DEBUGITEM(data7)
DEBUGITEM(a0)
...

I could see that nld_tms4800 rom wasn't outputting any data,
so after fixing that

Code
			else
			{
//				unsigned d = 0x00;   // doesn't actually output any data setting d to zero
				unsigned d = m_last_data;
				for (std::size_t i=0; i<4; i++)
				{
					if (m_OE1())
						m_D[i].push((d >> i) & 1, delay);
					if (m_OE2())
						m_D[i+4].push((d >> (i+4)) & 1, delay);
				}
			}
		}

[Linked Image from i.imgur.com]

It looks a little bit recognizable. I'm really confused by fixfreq.cpp and how it handles the sync so I see about one frame of screen then nothing.