HT9580 Datasheet, PDF (47/63 Pages) Holtek Semiconductor Inc – Character Pager Controller

Preliminary
HT9580
Mode
INX
INY
REL
Description
INDIRECT X: The byte following the opcode is added to the X register to produce a new
zero page address. The contents of this address and the following one are used as the
address to finally access the data. Note that when the X register is added to the byte
following the opcode, the upper byte of the address is always zero. {data=[(00,
IAL+X+1), (00, IAL+X)]}
INDIRECT Y: The byte following the opcode is a zero page address. The contents of
this location and the next one produce a 16-bit address which is then added to the Y
register to finally obtain the data. {data=<[(00, IAL+1), (00, IAL)]+Y>}
RELATIVE: The byte following the opcode is added in 2's complement fashion to the
PC. The byte is sign extended. Used by branching instructions.
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April 28, 2000