Overview

Interrupts

TODO

Roadmap

1. PS2 Keyboard
2. Timer
3. SPI, SD-Card
4. Sound card
5. Real-Time-Clock
6. MIDI (via FPGA)
7. Barcode Scanner (RS232 protocol)
8. GPIO
9. IO Break Out-Board

ISA

For further details see ISA Overview.

Mnemonic	Description
prefix_a16	change addressing mode to memory mapped IO for the next instruction
i2c_send	Send data over I2C
i2c_recv	Receive data over I2C
spi	send and receive for SPI communication

Control Lines

Note: We use ~ to denote active-low control lines. All other control lines are active-high.

Parallel

• ~INT: Signals CPU interrupt from IO-device.
• INTACK: Signals acknowledgement from CPU to IO-device. Commences interrupt handling routine.
• IO/MEM_TO_DBUS : Memory Write From Bus
• IO/MEM_FROM_DBUS: Memory Read From Bus
• ADDR16: Shared with Graphics to differentiate between MMIO and normal address space. The 17th address bit, so to say.
• BUSREQ: Signals CPU that IO-device wants to access data bus for read/write operation. For case IO to CPU: For case CPU to IO:

Serial (for SPI/I2C)

• SPI_SEND/REC: For sending and receiving data via SPI communication.
• SPI_SCLK_EN: Enables clock of SPI device to make SPI communication possible according to SPI protocol.

IO Address Ranges

Address	Device
0x0000	reserved
0x0001	Arduino
0x0008-0x000f	Keyboard
0x0100-0x01ff	Timer
0x8000-0xffff	Graphics-Card