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120 lines
4.5 KiB
Markdown
120 lines
4.5 KiB
Markdown
Using a combination of a 6522 along with some integrated circuits, the VIA Cuda is a microcontroller that heavily controls system operations. It's largely similar to Egret (used in many 68k Macs), but removes some commands.
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The usual offset for a VIA Cuda is IOBase (ex.: 0xF3000000 for Power Mac G3 Beige) + 0x16000. The registers are spaced out by 0x200 bytes on the Heathrow.
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# Usage
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The VIA Cuda is emulated in all Power Macs through an interrupt controller. Early Power Macs also used the Parameter RAM.
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Additionally, nodes are included for ADB peripherals, Parameter RAM, Real-Time Clocks, and Power Management.
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It can be run either synchronously or asynchronously.
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However, the CUDA is also slower than the CPU, thus causing a delay that the OS expects.
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# Registers
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Within the emulated CUDA, these registers are spaced apart by 0x200 bytes. Apple themselves recommended avoiding the usage of Handshake Data A.
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| Register Name |Abbreviation| Offset |
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|:-------------------------:|:----------:|:------:|
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| Data B | ORB | 0x0 |
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| Handshake Data A | ORA(H) | 0x1 |
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| Data Direction B | DIRB | 0x2 |
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| Data Direction A | DIRA | 0x3 |
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| Timer 1 Counter Low | T1C | 0x4 |
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| Timer 1 Counter High | T1CH | 0x5 |
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| Timer 1 Latch Low | T1L | 0x6 |
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| Timer 1 Latch High | T1LH | 0x7 |
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| Timer 2 Counter Low | T2C | 0x8 |
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| Timer 2 Counter High | T2CH | 0x9 |
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| Shift | SR | 0xA |
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| Auxiliary Control | ACR | 0xB |
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| Peripheral Control | PCR | 0xC |
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| Interrupt Flag | IFE | 0xD |
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| Interrupt Enable | IER | 0xE |
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| Data A | ORA | 0xF |
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## Data A
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| Register Bit | Bit Mask |
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|:----------------:|:--------:|
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| Drive Select | 0x10 |
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| Disk Head Select | 0x20 |
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## Auxiliary Control
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| Register Bit | Bit Mask |
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|:---------------------------------:|:--------:|
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| Port A Latch | 0x1 |
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| Port B Latch | 0x2 |
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| Timer 2, control | 0x20 |
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| Timer 1, continuous counting | 0x40 |
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| Timer 1, drives PB7 | 0x80 |
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## Interrupt Enable
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| Register Bit | Bit Mask |
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|:--------------:|:--------:|
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| CA2 | 0x1 |
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| CA1 | 0x2 |
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| Shift Register | 0x2 |
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| CB2 | 0x8 |
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| CB1 | 0x10 |
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| Timer 2 | 0x20 |
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| Timer 1 | 0x40 |
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| Set interrupt | 0x80 |
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# Packet Types
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| Hex | Packet Type |
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|:-------------:|:----------------------:|
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| 0x00 | ADB |
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| 0x01 | Pseudo |
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| 0x02 | Error |
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| 0x03 | Timer |
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| 0x04 | Power |
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| 0x05 | Mac II |
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# Device Commands
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| Hex | Device Command |
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|:-------------:|:----------------------:|
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| 0x00 | Reset Bus |
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| 0x01 | Flush ADB |
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| 0x08 | Write ADB |
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| 0x0C | Read ADB |
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# Pseudo Commands
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| Hex | Command Name |
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|:-------------:|:----------------------:|
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| 0x00 | WARM_START |
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| 0x01 | START_STOP_AUTO_POLL |
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| 0x02 | GET_6805_ADDRESS |
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| 0x03 | GET_REAL_TIME |
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| 0x07 | GET_PRAM |
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| 0x08 | SET_6805_ADDRESS |
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| 0x09 | SET_REAL_TIME |
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| 0x0A | POWER_DOWN |
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| 0x0B | SET_POWER_UPTIME |
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| 0x0C | SET_PRAM |
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| 0x0D | MONO_STABLE_RESET |
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| 0x0E | SEND_DFAC |
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| 0x10 | BATTERY_SWAP_SENSE |
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| 0x11 | RESTART_SYSTEM |
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| 0x12 | SET_IPL_LEVEL |
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| 0x13 | FILE_SERVER_FLAG |
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| 0x14 | SET_AUTO_RATE |
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| 0x16 | GET_AUTO_RATE |
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| 0x19 | SET_DEVICE_LIST |
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| 0x1A | GET_DEVICE_LIST |
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| 0x1B | SET_ONE_SECOND_MODE |
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| 0x21 | SET_POWER_MESSAGES |
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| 0x22 | GET_SET_IIC |
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| 0x23 | ENABLE_DISABLE_WAKEUP |
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| 0x24 | TIMER_TICKLE |
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| 0X25 | COMBINED_FORMAT_IIC |
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| 0x26 | (UNDOCUMENTED!) |
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