Imported from GitHub: Lougous/b68k-io · commit 8209d6e · license MIT

Description

IO extension board for b68k computer

README

b68k-io

IO extension board for b68k computer.

Features

• local bus peripheral to b68k-cpu computer
• a UART with DB9 connector (RS232, no hardware flow control)
• an I2C bus with onboard RTC chip (DS1307+) with crystal and backup battery, and 4-pins pin header extension connector
• a SPI bus with 7 chip select lines: 2x SD cards slots, 1x through an 8-pins pin header extension connector, 4x through DB15 connector for external equipements (external SPI slaves are electrically isolated from internal slaves)

Board fonctions are implemented with a PIC18F27K42 microcontroller.

The board has only two memory locations accessible through the expansion bus: one to set the actual register to access, the other to read or write data from/to the register.

register	address	description
DATA	XX0000h	register data
ADDRESS	XX0001h	register index

Register set

register	index	description
SPI_SEL	0	[5..3] : enabled SPI chip select line0: external #01: external #12: external #23: external #34: SD card A5: SD card B6: internal pin header7: none (reset)
SPI_CTRL	1	bit 7: BUSY rbit 2: CLRBF sbit 1: TXR rwbit 0: RXR rw
SPI_DATA	2	SPI data in/out
UART_STS	4	UART statusbit 7: TX readybit 1: RX FIFO overflowbit 0: RX FIFO underflow
UART_DATA	5	UART data in/out
I2C_CTRL	6	bit 7: RXIFbit 5: TXBEbit 2: resetbit 1: startbit 0: RXBF
I2C_CNT	7
I2C_DATA	8
I2C_CMD	9	bit 7..1: addressbit 0: RWn
IRQCFG	14	interrupt controller configurationbit 0: enable UART RX interrupt
IRQSTS	15	interrupt controller statusbit 0: UART RX interrupt pending