Echelon FT 3150 Smart Transceiver - Manual (Page 63)

FT 3120 / FT 3150 Smart Transceiver Data Book 57
Serial I/O Objects
Serial I/O Objects
The timing numbers shown in this section are valid for both an explicit I/O call or an implicit I/O call through a when
clause, and are assumed to be for a FT Smart Transceiver running at 10MHz.
Bitshift Input/Output
Pairs of adjacent pins may be configured as serial input or output lines. The first pin of the pair can be IO0-IO6, IO8,
or IO9, and is used for the clock (driven by the FT Smart Transceiver). The adjacent higher-numbered I/O pin is then
used for up to 16 bits of serial data. The data rate may be configured as 1kbps, 10kbps, or 15kbps at a 10MHz input
clock rate. The data rate scales proportionally to the input clock rate, for example: 4kbps, 40kbps, or 60kbps at a
40MHz input clock rate. The active clock edge may be specified as either rising or falling. This object is useful for
transferring data to external logic employing shift registers. This function suspends application processing until the
operation is complete. See Figures 3.22, 3.23, and 3.24.
For bitshift input, the clock output is deasserted (to the inactive level) at the same time as the start of the first bit of
data. For bitshift output, the clock output is initially inactive prior to the first bit of data (unless overridden by a bit
output overlay).
Figure 3.22 Bitshift I/O Examples
BITSHIFT OUTPUT
IO10
IO9
IO8
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
Clk
Data
Clk
Clk
Data
Clk
Data
Data
Clk
Data
BITSHIFT INPUT
IO10
IO9
IO8
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
Clk
Data
Clk
Clk
Data
Clk
Data
Data
Clk
Data