Description:

Pop the top two bytes off the stack as an I/O port reference.  Read a byte from the referenced port and push it onto the stack.

Pseudo Code:

portRef = stack[sp - 2]
sp = sp - 2
stack[sp] = port[portRef]
sp = sp + 1
pc = pc + 1

Flags Affected:

D	H	C	Z	N

Possible Errors:

tvmStackIOErr	-	The read operation from the memory-mapped IO port is invalid.
tvmStackUnderflow	-	There were not enough bytes in the stack to get the I/O Port reference.

Example:

pushmbx

Here the address for the aPortAddress port (0x0080) is on top of the stack (as an unsigned short) and we read the Module's address (0x02 in this example) as a byte and push it onto stack.

Before stack   top 1 0x80 2 0x00 3 0xAA 4 0x32 5 0x02   bottom

After stack   top 1 0x02 2 0xAA 3 0x32 4 0x02   bottom