Differences

This shows you the differences between two versions of the page.

--- documentations:devices:6809 [2014/04/10 21:49] – [Instruction set and addressing modes] pulkomandy
+++ documentations:devices:6809 [2015/02/28 18:08] (current) – external edit 127.0.0.1
@@ Line 3: / Line 3: @@
 ===== Technical description =====
-Registers:
+==== Registers ====
-* A and B: two 8-bit accumulators, useable as the 16-bit D
+   * A and B: two 8-bit accumulators, useable as the 16-bit D
-* X and Y: two index registers, used as memory pointers
+   * X and Y: two index registers, used as memory pointers
-* U and S: user and system stacks
+   * U and S: user and system stacks
-* CC: condition flags register
+   * CC: condition flags register
-* DP: direct-page pointer
+   * DP: direct-page pointer
 ==== Instruction set and addressing modes ====
 This is already covered elsewhere on the internet. Do I need to repeat everything?
-* [[http://public.logica.com/~burgins/emulator/com/m6809.html]] - Opcode summary with number of cycles, hex encoding of instruction, and brief description.
-* [[http://www.maddes.net/m6809pm/]] - HTML version of the 6809 programming manual, more verbose, with cycle-by-cycle execution diagrams of all instructions.
+  * [[http://techheap.packetizer.com/processors/6809/6809_instruction_set.html]] - Opcode summary with number of cycles, hex encoding of instruction, and brief description.
+  * [[http://www.maddes.net/m6809pm/]] - HTML version of the 6809 programming manual, more verbose, with cycle-by-cycle execution diagrams of all instructions.
+  * [[http://www.playvectrex.com/designit/lecture/MICROS.HTM]] - 6809 programming course
 ====Interrupts====
   * Reset: at system reset.
   * NMI: non-maskable.
-  * IRQ
+  * IRQ: all registers are saved on the stack before processing the interrupt.
-  * FIQ: registers are not automatically saved (faster than IRQ, but needs manual save of used registers)
+  * FIQ: Only PC and CC are saved (faster than IRQ, but needs manual save of registers used in the IRQ handler).
-  * SWI1, 2, and 3: software interrupts triggered by the SWI instruction.
+  * SWI1, 2, and 3: software interrupts triggered by the SWI instructions. (On Thomson machines with standard ROM, only SWI1 is useable, the others are hardcoded to do nothing).
+The 6809 interrupts fetch an address from memory, and jumps to it. The interrupt table is at a fixed address at the top of memory:
+  * FFF2: SWI3
+  * FFF4: SWI2
+  * FFF6: FIRQ
+  * FFF8: IRQ
+  * FFFA: SWI
+  * FFFC: NMI
+  * FFFE: Reset
 ===== Download =====
-Datasheet, programming manual
+  * Complete programming manual as PDF
+  * {{:documentations:devices:m6809pm_html.zip|Programming manual, partial HTML version}}
+  * Datasheet