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NuBusFPGA
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Romain Dolbeau 2023-05-22 08:53:45 +02:00
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@ -14,18 +14,17 @@ First prototype is working in a Quadra 650, running MacOS 8.1. It implements a s
Some basic acceleration now exists for 8/16/32 bits, doing rectangle screen-to-screen blits and pattern rectangle fills. 1/2/4 bits also has some acceleration, but only for byte-aligned cases.
There's also a basic RAM Disk using the 248 MiB of SDRAM not used by the framebuffer. The driver can use either synchronous direct access to the memory bt the CPU, or asynchronous using DMA (using 16-bytes blocks). Frustratingly, the direct access methode seems faster.
There's also a basic RAM Disk using the 248 MiB of SDRAM not used by the framebuffer. The driver can use either synchronous direct access to the memory by the CPU, or asynchronous using DMA (using 16-bytes blocks). Frustratingly, the direct access methode seems faster.
## The hardware
Directory 'nubus-to-ztex'
The V1.0 custom board is a NuBus-compliant (I hope...) board, designed to receive a [ZTex USB-FPGA Module 2.13](https://www.ztex.de/usb-fpga-2/usb-fpga-2.13.e.html) as a daughterboard. The ZTex module contains the actual FPGA (Artix-7), some RAM, programming hardware, etc. The NuBus board contains level-shifters & drivers ICs to interface between the NuBus signals and the FPGA, a CPLD handling some level-shifting & the bus mastering arbitration, a serial header, two user Leds, 14 debug Leds tied to specific NuBus or CPLD/FPGA signals, a JTAG header, a USB micro-B connector, a VGA chip & connector, and a HDMI chip & connector. It supports every NuBus feature except the optional parity (i.e. it can do both slave and master modes).
The (now obsolete) V1.0 custom board is a NuBus-compliant (I hope...) board, designed to receive a [ZTex USB-FPGA Module 2.13](https://www.ztex.de/usb-fpga-2/usb-fpga-2.13.e.html) as a daughterboard. The ZTex module contains the actual FPGA (Artix-7), some RAM, programming hardware, etc. The NuBus board contains level-shifters & drivers ICs to interface between the NuBus signals and the FPGA, a CPLD handling some level-shifting & the bus mastering arbitration, a serial header, two user Leds, 14 debug Leds tied to specific NuBus or CPLD/FPGA signals, a JTAG header, a USB micro-B connector, a VGA chip & connector, and a HDMI chip & connector. It supports every NuBus feature except the optional parity (i.e. it can do both slave and master modes). The V1.0 board is in commit 3f3371a. The CPLD solution works but is annoying as it requires older Xilinx software (ISE 14.7) and dedicated JTAG programmer to use.
The current board is V1.2. It drops the CPLD and VGA port. Bus arbitration is now done inside the FPGA. It gains a micro-sd slot, and a custom expansion connector that is based (and compatible with, with more signals) PMod. It supports the same accelerated HDMI framebuffer and RAM Disk. Optionally, The Declaration Rom can be stored in a Flash NOR chip connected ot the PMOd expansion connector (easier for working on embedded driver in the DeclRom).
The V1.0 board is in commit 3f3371a. The CPLD solution works but is annoying as it requires older Xilinx software (ISE 14.7) and dedicated JTAG programmer to use. A revision V1.2 board is in the work but not yet made, which will remove the VGA connector and CPLD (and require more dedicated level-shifters/drivers) and replace them by a micro-sd card slot and an expansion connector (Pmod-like).
The PCB was designed with Kicad 5.0
The PCBs were designed with Kicad 5.1
## The gateware (Migen)