Universal IO expander (UNIO)

Two ports, one 6 bit control port and one 8 bit io port. The power up reading of the control port (with weak pull up's) tells the UNIO what mode to operate in. Modes that do not use all 6 control port lines are identified because they have the left over lines pulled (or jumpered) low on the circuit board.

initial reading	Signals	Mode	Notes
111111	En, Addr, Data[4]	4 bit by two addressable latch
011111	-, Addr, Data[4]	4 bit by two addressable latch	Lack of clock is compinsated for by watching all lines for 0.5 clock cycles after any change is detected and updateing output pins only after this "settleing time"
1110 11	En, Data[2], -, Addr[2]	2 bit by four addressable latch
0110 11	-, Data[2], Addr[2]	2 bit by four addressable latch
101 111	En, -, Data, Addr[0..3]	1 bit by eight addressable latch
010 111	-, Data, -, Addr[0..3]	1 bit by eight addressable latch
1111 10	SCK, SI, SO, *CE, 1, 0	SPI
1011 10	SCK, -, SI+SO, CE, 1, 0	SPI (3 pin)	SO connected to SI thru resistor
1111 00	SCK, SI, SO, CE, 0, 0	SPI <-> Serial	RX, TX, *CE, are the first three pins of the 8 bit IO port
1111 01	SCK, SI, SO, CE, 0, 1	SPI <-> I2C	SCL, SDA, -, *CE are the first four pins of the 8 bit IO port.
1100 01	SCL, SDA, -, -, 0, 1	I2C	Basically a shift register
1101 01	SCL, SDA, -, *CE, 0, 1	I2C with *CE	Several shift registers connect to the same data and clock lines with seperate chip selects
1111 01	SCL, SDA, CLR, *CE, 0, 1	I2C with *CE and CLR	Shift register with enable and clear.
1101 00	SCL, SDA, -,*CE, 0 , 0	I2C <-> Serial	Allows us to debug I2C interfaces. When the Serial CE line is asserted, data is copied from RX to SDA and clocked at the baud rate established by an inital "AT" sent to RX with CE deasserted. Any I2C signals recieved on SDA while the serial CE is no asserted will be transmitted to TX at 2400 baud or at a rate indicated by an "AT" sent to RX. RX, TX, CE, are the first three pins of the 8 bit IO port This mode can also be entered from any of the other I2C modes by dropping the last bit of the control port to 0 from 1. Care should be taken because the Serial TX line will immediatly be driven by the chip and the Serial *CE line could drive SDA and SCL if it is held low.
0100 00	-, TX, -, -, 0, 0	Serial Out
1000 00	RX, -, -, -, 0, 0	Serial In
0110 00	-, TX,*CE, -, 0, 0	Serial Out with *CE
1010 00	RX, -, *CE, -, 0, 0	Serial In with *CE
1100 00	RX, TX, -, -, 0, 0	Serial IO
1110 00	RX, TX, *CE, -, 0, 0	Serial IO with *CE

Notice that the first line of the 6 bit control port is the IRQ line.

file: /Techref/idea/unio.htm, 4KB, , updated: 2002/5/6 15:26, local time: 2024/12/26 21:43,

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