MUTIF09 I/O Expansion Board (MUTIF09-IOEXP)

Revision 3, works as expected (May 21, 2019)

MUTIF09 I/O Expansion Board is designed to add I2C (5V and 3.3V), SPI (3.3V) and GPIO (data pins are 5V tolerant but 3.3V is preferable) connectivity and functionality via TTL serial connection. Basically, this board is intended for use together with the MUTIF09 6809 SBC but theoretically it can work with other single board computer with minimal modification.

MUTIF09 6809SBC sees this board as an additional asynchronous communication interface adapter (ACIA) and this board works as an interface between ACIA and the I2C- & SPI-bus. This allows the 6809 to communicate with other I2C- or SPI-bus deveices such as temperature sensor, Realtime clock, EEPROM, ADC, SRAM and so on through ACIA.

Block Diagram

(You may need to install an extension, like mermaid-for-github-chrome-extension (for Google Chrome) to see this diagram correctly)

graph TD
  id0>MUTIF6809 SBC] --- 16550
  16550 --- id1[Level Shifter]
  id1 --- SC18IM700
  SC18IM700---|MST0|PCA9541
  PCA9541---|Slave|id2[I2C-Level Shifter]
  id2 --- id3[5V I2C Slave port]
  PCA9541---|Slave|id4[3.3V I2C Slave port]
  PCA9541---|Slave|id5["on board RTC (DS3231)"]
  id6>External I2C Master] --- ADuM1250
  ADuM1250---|MST1|PCA9541
  SC18IM700 --- SCIS602B
  SC18IS602B --- id7[SPI slave port]
  SC18IM700 --- id8["GPIO port (8 bits)"]

Feature	Status	Implemented by using
Additional UART w/ FIFO	works	16550
UART-I2C (3.3 V, 5 V) bridge	works	SC18IM700, BSS138
UART-SPI (3.3 V) bridge	works	SC18IM700, SC18IS602B
GPIO (8 bit, 3.3 V)	works	SC18IM700
I2C-bus master selection	works	PCA9541
On-board RTC	works	DS3231 w/ backup battery

Memory Maps

Address	Register
$B020	Receiver Buffer Reg. /Transmitter Holding Reg.
$B021	Interrupt Enable Reg./Interrupt Indent. Reg.
$B022	FIFO Control Reg.
$B023	Line Control Reg.
$B024	MODEM Control Reg.
$B025	Line Status Reg.
$B026	MODEM Status Reg.
$B027	Scratch Reg.
$B020	Divisor Latch (Lo byte) if MSB of Line Control Reg. is 1
$B021	Divisor Latch (Hi byte) if MSB of Line Control Reg. is 1

Documentation

This board has many features and therefore, I think that it needs documentation and examples. In this regard, I wrote a booklet about this and it will be available on the 4th day (August 12) of Comic Market 96 (Ariake, Tokyo, Japan) at booth# 南ラ13b and at BOOTH ( https://m-nihombashi.booth.pm/ ) thereafter. For now, please refer to the corresponding datasheets.