Immediate Mode - Revision history

Mr z: Protected "Immediate Mode" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T08:35:27Z

Protected "Immediate Mode" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

Mr z at 09:10, 7 October 2007

2007-10-07T09:10:19Z

Mr z at 22:19, 14 January 2005

2005-01-14T22:19:59Z

Mr z: /* put in actual opcode value for MVI@ */

2005-01-14T22:17:09Z

‎put in actual opcode value for MVI@

Pingaso at 21:26, 14 January 2005

2005-01-14T21:26:55Z

Pingaso at 21:26, 14 January 2005

2005-01-14T21:26:46Z

Mr z at 20:00, 12 January 2005

2005-01-12T20:00:46Z

New page

[[Immediate Mode]] instructions read (or write) one of their arguments from memory immediately following the instruction. It appears the [[CP1610]] actually implements [[Immediate Mode]] as an [[Indirect Mode]] access, using R7 (the program counter) as the indirection register.

[[Immediate Mode]] instructions ordinarily access one word at the specified location. The [[Double Byte Data Flag]] modifies [[Immediate Mode]] instructions that read memory. Thus, the constant that follows such an instruction occupies two words of memory instead of one. For example:

; Example with Double Byte Data Flag cleared
MVII #$0123, R0
encodes to:
$0xxx ; MVI@ R7, R0 opcode
$0123 ; the immediate constant $0123

Compare that to:

; Example with Double Byte Data Flag set
SDBD
MVII #$0123, R0
encodes to:
$0001 ; SDBD opcode
$0xxx ; MVI@ R7, R0
$0023 ; lower 8 bits of immediate constant $0123
$0001 ; upper 8 bits of immediate constant $0123

@@ Line 6: / Line 6: @@
      MVII #$0123, R0<br/>
   encodes to:<br/>
-     $0xxx   ; MVI@ R7, R0 opcode
+     $02B8   ; MVI@ R7, R0 opcode
      $0123   ; the immediate constant $0123

@@ Line 1: / Line 1: @@
-Immediate Mode instructions read (or write) one of their arguments from memory immediately following the instruction.  It appears the [[CP1610]] actually implements Immediate Mode as an [[Indirect Mode]] access, using R7 (the program counter) as the indirection register.
+Immediate Mode instructions read (or write) one of their arguments in memory immediately following the instruction.  It appears the [[CP1610]] actually implements Immediate Mode as an [[Indirect Mode]] access, using R7 (the program counter) as the indirection register.
 Immediate Mode instructions ordinarily access one word at the specified location.  The [[Double Byte Data Flag]] modifies Immediate Mode instructions that read memory.  Thus, the constant that follows such an instruction occupies two words of memory instead of one.  For example:
@@ Line 19: / Line 19: @@
      $0023   ; lower 8 bits of immediate constant $0123
      $0001   ; upper 8 bits of immediate constant $0123

@@ Line 1: / Line 1: @@
 Immediate Mode instructions read (or write) one of their arguments from memory immediately following the instruction.  It appears the [[CP1610]] actually implements Immediate Mode as an [[Indirect Mode]] access, using R7 (the program counter) as the indirection register.
-Immediate Mode instructions ordinarily access one word at the specified location.  The [[Double Byte Data Flag]] modifies [[Immediate Mode]] instructions that read memory.  Thus, the constant that follows such an instruction occupies two words of memory instead of one.  For example:
+Immediate Mode instructions ordinarily access one word at the specified location.  The [[Double Byte Data Flag]] modifies Immediate Mode instructions that read memory.  Thus, the constant that follows such an instruction occupies two words of memory instead of one.  For example:
      ; Example with Double Byte Data Flag cleared

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