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base:rr-net_memory_map_docs [2015-04-17 04:33]
base:rr-net_memory_map_docs [2015-04-17 04:33] (current)
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 +====== RR-net memory map & docs ======
 +This document is freely distributable as long as it is not changed, and one
 +of the sources,,
 +or is mentioned. 
 +last update:
 +august 31st, 2003: initial release
 +RR-Net is a 10MBit networking card that is designed for the commodore C64,
 +for use on the Retro Replay freezer cartridge. It'll also work on the Amiga
 +with a clock-port, but it is not recommended: The card does not support IRQs,
 +and it hardly fits mechanically. If you need network for your Amiga, use the
 +X-Surf 2 board.
 +Memory map
 +The memory map depends on the place where RR-Net is connected. Although
 +RR-Net is designed for the C64, here are also the offset addresses for the
 +Amiga. Check the corresponding hardware documentations for the carrier cards
 +to obtain the base addresses of the clockport.
 +RR-Net is based on the Cirrus logic CS8900a (Crystal LAN). The chip is used
 +in 8-bit mode, so the 8 registers of an NE2000 are spread over 16 registers
 +in an 8-bit system. The 8-bit mode of the chip does not support IRQs (see
 +Cirrus logic application note AN181).
 +Do not forget to switch on the accessory connector of the Retro Replay by
 +setting bit 0 in $de01. See Inside_Replay.txt for more information.
 +C64 register    Amiga register  read/write      meaning
 +none            $00/$04         read-only       interrupt status queue
 +$de02/$de03     $08/$0c         read/write      PackatPage pointer
 +$de04/$de05     $10/$14         read/write      PacketPage Data (Port 0)
 +$de06/$de07     $18/$1c         read/write      PacketPage Data (Port 1)
 +$de08/$de09     $20/$24         read/write      Receive/Transmit Data (Port 0)
 +$de0a/$de0b     $28/$2c         read/write      Receive/Transmit Data (Port 1)
 +$de0c/$de0d     $30/$34         write-only      TxCMD (Transmit Command)
 +$de0e/$de0f     $38/$3c         write-only      TxLength (Transmit Length)
 +Although the Amiga makes the interrupt status queue registers available, it
 +does not have any effect. Even if you try to activate the chip's IRQ features,
 +it will not have any effect. The IRQ line of the chip is not wired on RR-Net
 +at all!
 +If you compare this register map to the register map in AN181, you might
 +notice that the first and the second half of the register set is swapped.
 +This has been done, because the accessory connector of the Retro Replay does
 +not provide the full range of registers available on the Amiga clockport. The
 +first two bytes are control registers of the freezer cartridge, and this
 +swapping moves the unnecessary register-pair (IRQ status queue) into the
 +"invisible" area of the cartridge.
 +Although the chip is used in 8-bit mode, you have to know the endianess,
 +because each register pair forms a one 16-bit register. Ethernet is
 +big-endian by default. The chip was designed as an ISA thing, so all
 +registers appear as little endian. In other words: The lowbyte comes first,
 +then the highbyte.
 +MAC address
 +RR-Net does not have an EEprom to store the MAC address, so it should be
 +stored somewhere else: The flash rom of Retro Replay, the disk of the
 +Contiki operating system by Adam Dunkels (,
 +or Kickflash OS4 for the Amiga. The Mac address is only needed when
 +transmitting packets, so it's OK if it's loaded from mass storage media when
 +loading/starting the driver. The Mac address is NOT needed when RR-Net is
 +just connected to other networking equipment. The LINK led might already be
 +on, but the MAC address is only needed when something is transmitted into the
 +More literature
 +Cirrus Logic Application note AN181: "Using the Crystal CS8900A in 8-bit
 +mode" by James Ayres:
 +Crystal LAN CS8900A Ethernet Controller Technical Reference manual AN83:
 +The product data sheet for the CS8900A also contains software information,
 +starting at chapter 4 (page 38):
 +Application note 194: "How to program the Hash filter in the CS8900A":
 +The FAQ about the chip:
 +Fine print
 +RR-Net is not designed, authorized or warranted to be suitable for use in
 +life-support devices or systems or other critical operations. Inclusion of
 +the product in such applications is understood to be fully at the
 +customer's risk.
 +** EOF
base/rr-net_memory_map_docs.txt ยท Last modified: 2015-04-17 04:33 (external edit)