HMCS404C----------------------------------------------------------------
• RAM ADDRESSING MODE
As shown in Fig. 21, the MeV provides three RAM address-
ing modes; Register Indirect Addressing, Direct Addressing and
Memory Register Addressing.
• Register Indirect Addressing
The combined lO-bit contents of W Register, X Register and
Y Register is used as the RAM address in this mode.
RAM Address
• Direct Addressing
The direct addressing instruction consists of two words and
the second word (10 bits) following Op-code (the first word) is
used as the RAM address.
• Memory Register Addressing
The Memory Register Addressing can access 16 digits
(Memory Register: MR) from $020 to $02F by using the LAMR
and XMRA instruction.
W-Register
X-Register
Y -Register
,--------...,r--------..\r"---=----.....
(a) Register Indirect Addressing
Instruction 1 st Word
Instruction 2nd Word
(b) Direct Addressing
Instruction
"0" "0"
"0" "0"
"1" "0"
RAM Address
(e) Memory Register Addressing
Fig. 21
RAM Addressing Mode
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