User:Lidnariq/Mapper thoughts: Difference between revisions

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(ok, use NAND4 instead of NAND3 to fit back into 4 discrete-logic ICs.)
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==EtherNES 1==
==EtherNES 1==
A cartridge designed to provide ethernet is as simple a manner as practical, for use with [http://www.contiki-os.org/ Contiki]. The design is intentionally similar to a C64 ethernet cartridge, even though the CS8900A is comparatively expensive.
A cartridge designed to provide ethernet in as simple a manner as practical, for use with [http://www.contiki-os.org/ Contiki]. The design is intentionally similar to the [http://www.go4retro.com/products/64nic/ 64NIC+ ethernet cartridge for the Commodore 64], even though the CS8900A is comparatively expensive.


===Parts===
===Parts===
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** Other NAND4 produces /RD.
** Other NAND4 produces /RD.
** 2nd decoder selects RAM or ROM as appropriate.
** 2nd decoder selects RAM or ROM as appropriate.
* CS8900A (or possibly RTL8029)
* CS8900A or LAN91C96 (or possibly RTL8029, but only the first two have already-in-tree ethernet drivers)
* Ethernet transformer
* Ethernet transformer
See also http://www.go4retro.com/products/64nic/


===Memory map===
===Memory map===

Revision as of 01:47, 13 March 2015

EtherNES 1

A cartridge designed to provide ethernet in as simple a manner as practical, for use with Contiki. The design is intentionally similar to the 64NIC+ ethernet cartridge for the Commodore 64, even though the CS8900A is comparatively expensive.

Parts

  • 1 × SST39SF010A, 128 KiB FLASH EEPROM, for booting
  • 2 × AS6C1008, 128 KiB static RAM, one each for PRG RAM and CHR RAM
  • 2 × 74'161, both set up to clear on reset.
    • One selects a 32 KiB slice of PRG
    • The other selects an 8 KiB slice of CHR RAM.
  • 1 × 74'139
  • 1 × 74'20
    • One NAND4 produces /INTSEL=NAND3(M2,/ROMSEL,A14,A13) and one decoder produces /RD6xxx, /WR6xxx, /RD7xxx, and /WR7xxx.
    • Other NAND4 produces /RD.
    • 2nd decoder selects RAM or ROM as appropriate.
  • CS8900A or LAN91C96 (or possibly RTL8029, but only the first two have already-in-tree ethernet drivers)
  • Ethernet transformer

Memory map

  • $6xxx - CS8900A
    • http://www.cirrus.com/en/products/cs8900a.html
    • As with the C64 NIC, it does not present the memory-mappable portion of the CS8900A
    • CS8900A does not have a separate I/O enable, just /IOR and /IOW; address bus must be stable before these signals fall: Thus, /RD6xxx and /WR6xxx are connected to the CS8900A
    • Why does the 64NIC+ not connect /IRQ ?
    • Obviously no DMA support either. (Do we want to support OAM DMA from ethernet?)
  • READS from $7xxx - latching CPU A0..A3: PRG bank '161 (0,1,2,3 = ROM; C,D,E,F=RAM). Q3 determines which IC. Cleared on hardware reset.
  • WRITES to $7xxx - latching CPU D0..D3: CHR bank '161
  • $8000-$FFFF: PRG ROM or RAM, according to value at $7xxx.