4-2
4
switch if it is enabled, set the Digital I/O lines to their saved configuration,
set the Relay Drivers to their saved condition , the Analog Outputs to their
saved vales and use the saved configuration values to operate the unit.
The 4867's Digital I/O Interface consists of four 8-bit ABT latches which can
be individually set as inputs or outputs. As inputs, each lines has a 33 Kohm
pullup resistor to +5 Vdc and is designed to accommodate contact closures,
TTL logic inputs or CMOS logic inputs. As outputs, each line is latched and
holds the last value written to it unit changed. There are no glitches when
the latches are updated. The latches provide high power TTL output signals
that can sink 48 mA or source 24 mA. Use a resistor with a minimum value
of 1000 ohms when connecting the latched outputs directly to another 4867
Figure 4-1 4867 Block Diagram
Microprocessor
Address
DCDR
GPIB
4 Analog
Outputs
4
8 Ch
Mux
A/D
Conv
RAM
µP BUS
Flash
Memory
32
Digital
I/O Lines
Buffer/
Registers
6 Driver
Outputs
Latch
6 Analog
Inputs
LED
Latch
Status
LEDs
4 Ch
Mux
Temp Conv
4 TC
Inputs
GPIB
Intfc
Power
Supply
9-32 VDC
+5V
