Echelon I/O Model Reference for Smart Transceivers and Neuron Chips - Manual (Page 92)

82 Serial I/O Models
Symbol Description Minimum Typical Maximum
t
start
End of start condition
io_in()
io_out()
5.4 μs
5.4 μs
— —
t
cla
End of start to start of address
io_in()
io_out() 24.0 μs
24.0 μs
— —
t
cld
SCL low to data for io_out() 24.6 μs — —
t
dch
Data to SCL high for io_out() 7.2 μs — —
t
chcl
Clock high to clock low for io_out() 12.6 μs — —
t
chd
SCL high to data sampling for io_in() 13.2 μs — —
t
dcl
Data sample to SCL low for io_in() 7.2 μs — —
t
clch
Clock low to clock high for io_in() 24.0 μs — —
t
stop
Clock high to data
io_in()
io_out()
12.6 μs
12.6 μs
— —
t
ret
SDA high to return from function
io_in()
io_out()
— —
4.2 μs
4.2 μs
Programming Considerations
The i2c I/O object can be declared with pin IO_8 as the serial clock (SCL) line,
and pin IO_9 as the serial data (SDA) line, or it can be declared with pin IO_0 as
the serial clock line, and pin IO_1 as the serial data line. The Neuron Chip or
Smart Transceiver acts as a master only. Two external pull-ups are required,
and the interface is connected directly to the I/O pins. These I/O pins are
operated as open-drain devices in order to support the interface.
An i2c I/O object declared on pin IO_8 can be declared with the
use_stop_condition option keyword. This option allows for combined format data
transfers. For example, you can address and write to a peripheral device with
one or more io_out( ) calls with stop set to FALSE, followed by a call to io_out( )
with stop set to TRUE to finish the transfer with the STOP condition.
For all transfers, an I
2 C device address argument is required. This byte must be
the right-justified 7-bit I 2 C device address. Up to 255 bytes of data can be
transferred at a time. The address is written to the bus at the start of any
transfer, immediately following the I 2 C bus start condition. A count argument is
also required; this controls how many data bytes are to be written or read.