understanding port and peripherals

OK - LCD & keypad will work on P1, but neither LCD or keypad will work on P0.

I see a few potential problems here. I would try to use P0 the same way you used P1. That is, skip using the XBYTE macro and manipulate P0 directly for the LCD. As long as make sure P2.7 (A15) remains high, your RAM & ROM should stay off the bus (assuming your chip select logic only enables RAM or ROM below 0x8000)

Then write your code like this:
//if P0, RD, WR, A15 are not yet defined
// define them here
#define P0 0x80
#define RD 0xB7
#define WR 0xB6
#define A15 0xA7
void Data_Write(unsigned char character)
{
A15 = 1;//this turns off RAM & ROM
CS_LCD = 1;//if active hi or 0 if active low
//assert anything else that the LCD
//needs asserted here
WR = 0; //assert write signal
P0 = character; //put data on bus
WR = 1; //deassert write signal
CS_LCD = 0;//if active hi or 1 if active low
//deassert everything asserted above here
P0 = 0xFF; //maybe not needed - but doesn't hurt
}
unsigned char Read_Data(void)
{
unsigned char Read_bus;
A15 = 1;//turns off RAM & ROM
CS_LCD = 1;//if active hi or 0 if active low
//assert anything else that the LCD
//needs asserted here
P0 = 0xFF;//prime data bus
RD = 0;//assert read signal
Read_bus = P0; //data is on bus, get it
RD = 1;//deassert read signal
CS_LCD = 0;//if active hi or 1 if active low
//deassert anything asserted above here
return (Read_bus);
}

With no scope or logic analyzer, you can debug your signals with a multimeter by inserting an endless loop in your code immediately after the instruction that you are interested in.

Use

while(1)
;

for your endless loop.

Essentially, your setup is "frozen" in the state it was in right before it went into the endless loop. You can then use a regular old multi-meter to see what signals are high and what signals are low.
This works, but can be tedious since you have to constantly reprogram the code when you want to move the loop or take it out completely.

You can use XBYTE if you want to. But, understand that the read or write takes place entirely "within" that instruction. In other words, you need to make sure that you assert everything that must be asserted and then do the XBYTE then deassert the LCD stuff.
Or, if using the GAL to generate your chip selects - fix your CS_LCD equation.

CS_LCD = !A15#(RD&WR);//CS_LCD active low
CS_LCD = A15&(!RD#!WR);//CS_LCD active hi

By the way, getting both the LCD and keypad working on P1 is pretty sophisticated for a Newbie. You are getting close!

Good luck.

OK - LCD & keypad will work on P1, but neither LCD or keypad will work on P0.

I see a few potential problems here. I would try to use P0 the same way you used P1. That is, skip using the XBYTE macro and manipulate P0 directly for the LCD. As long as make sure P2.7 (A15) remains high, your RAM & ROM should stay off the bus (assuming your chip select logic only enables RAM or ROM below 0x8000)

Then write your code like this:
//if P0, RD, WR, A15 are not yet defined
// define them here
#define P0 0x80
#define RD 0xB7
#define WR 0xB6
#define A15 0xA7
void Data_Write(unsigned char character)
{
A15 = 1;//this turns off RAM & ROM
CS_LCD = 1;//if active hi or 0 if active low
//assert anything else that the LCD
//needs asserted here
WR = 0; //assert write signal
P0 = character; //put data on bus
WR = 1; //deassert write signal
CS_LCD = 0;//if active hi or 1 if active low
//deassert everything asserted above here
P0 = 0xFF; //maybe not needed - but doesn't hurt
}
unsigned char Read_Data(void)
{
unsigned char Read_bus;
A15 = 1;//turns off RAM & ROM
CS_LCD = 1;//if active hi or 0 if active low
//assert anything else that the LCD
//needs asserted here
P0 = 0xFF;//prime data bus
RD = 0;//assert read signal
Read_bus = P0; //data is on bus, get it
RD = 1;//deassert read signal
CS_LCD = 0;//if active hi or 1 if active low
//deassert anything asserted above here
return (Read_bus);
}

With no scope or logic analyzer, you can debug your signals with a multimeter by inserting an endless loop in your code immediately after the instruction that you are interested in.

Use

while(1)
;

for your endless loop.

Essentially, your setup is "frozen" in the state it was in right before it went into the endless loop. You can then use a regular old multi-meter to see what signals are high and what signals are low.
This works, but can be tedious since you have to constantly reprogram the code when you want to move the loop or take it out completely.

You can use XBYTE if you want to. But, understand that the read or write takes place entirely "within" that instruction. In other words, you need to make sure that you assert everything that must be asserted and then do the XBYTE then deassert the LCD stuff.
Or, if using the GAL to generate your chip selects - fix your CS_LCD equation.

CS_LCD = !A15#(RD&WR);//CS_LCD active low
CS_LCD = A15&(!RD#!WR);//CS_LCD active hi

By the way, getting both the LCD and keypad working on P1 is pretty sophisticated for a Newbie. You are getting close!

Good luck.