Filter
Top Products
L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 207
Synchronous Buffered Inputs You can use synchronous mode handshake with
buffered (memory) input operations. (Buffered operations are described in
more detail beginning on page 210.) For buffered input operations, the H0
line acts as a start/stop line. This line will be set high when the memory
input command is executed and will return low when the memory input
operation has completed. The H1 line is not used and is set to high
impedance.
An external strobe input on the H2 line controls the pace of memory transfers.
The sending device must ensure the data is valid before the T
SETUP
and stays
valid until after T
HOLD
. T
SETUP
is 30 ns and T
HOLD
is
55 ns.
A synchronous buffered input using an external clock is shown in the diagram
below (default handshake line polarity).
For example, the following SCPI commands set the L4450A to have an 8- bit
input using synchronous handshake with an external strobe input. The
number of bytes to read into memory is set to infinite (continuous reading into
memory until the memory is stopped). The memory is enabled and then
triggered. The start/stop line is set high following the first byte handshake and
remains high until the last byte is captured.
CONF:DIG:WIDT BYTE, (@1101)
CONF:DIG:DIR INP, (@1101)
CONF:DIG:HAND SYNC, (@1101)
SENS:DIG:MEM:SAMP:COUN 0, (@1101)
SENS:DIG:MEM:ENAB ON, (@1101)
SENS:DIG:MEM:STAR (@1101)
H0 (Start/
Stop)
H2 (Strobe In)
Data In
Valid Don't-Care
T
SETUP
T
HOLD
T
CYCLE
>
100 ns
T
SETUP
T
HOLD
Valid
(Last Cycle)
Don't-Care Don't-Care Don't-CareValid
> 50 ns