Specifications

PK2100 Series Z-World 530-757-3737 5
positive and negative inputs will be exactly 1 and will not de-
pend on a balance between resistors, making the output 5 volts
when both differential inputs are 5 volts.
If the gain is increased, it becomes necessary to use an opera-
tional amplifier with a more stable offset voltage than the
LM324, which has considerable drift over temperature. The
Linear Technology LM1014 is suitable for gains up to 100 or
more. The negative input has a low input impedance compared
to the positive input (when H7 is removed). If R5 is decreased
to increase the gain, this impedance becomes even lower. When
a bridge is used, the finite impedance of the negative input has
the effect of changing the gain slightly.
Digital Inputs
The 7 digital inputs accept an input voltage with a digital
threshold at approximately 2.5 volts. The inputs are protected
against overload over the range of –48 to +48 volts.
+5V
0.01 µF
Digital Input
22k
Input
10k
low-pass
filter
These inputs are convenient for detecting contact closures or
sensing devices with open collector transistor outputs. Logic
level outputs can also be detected if they are supplied from
CMOS logic outputs which are guaranteed to swing to at least
3.5 volts. Three of the digital inputs (D5–D7) also function as
inputs to the high speed counters.
Counter Inputs
Three of the digital inputs also serve as counter inputs. There
is, in addition, a special differential counter input. The counter
inputs are arranged as shown here:
+
–
Differential receiver
+5V
C1A
+5V
C1B
+5V
C2A
C2B+
C2B–
C2B
/DREQ0
/DREQ1
CKA1
Counter 1
Counter 2
J8:7-8
J8:9-10
U34
The counters sense negative edges. The differential receiver in-
put can be used as a digital input by attaching one side of it to
the desired threshold voltage. It can be used as a true differen-
tial input for such devices as inductive pickups. It has a com-
mon mode voltage range from –12 to +12 volts with an input
hysteresis of 50 millivolts. An internal jumper can connect the
signal CKA1 which is controlled by the serial port hardware. It
can be set to various speeds from 600 kHz down to 300 Hz.
The counters use the DMA channels of the Z180. The maximum
counting speed is approximately 600 kHz. The DMA channel
can be programmed to store a byte from an I/O port to memory
for each count, if desired. This byte can be the least significant
byte of the internal programmable counter (PRT) which allows
the count edge to be localized in time. This feature can also de-
termine the exact time, within a few microseconds, at which an
event occurs by programming the DMA channel to store one
byte and then interrupt. The interrupt routine can read the most
significant part of the PRT counter and any software extension
of this counter. In general, the maximum count is 65,536 which
can be extended by software to larger counts if the counting
speed is not higher than about 10 kHz.
The capabilities of the counter are summarized as follows:
1 Measure the time at which a negative edge occurs with a
precision of a few microseconds. The measurement can be
repeated hundreds of times per second. A minimum time
must occur between successive events to allow for interrupt
processing.
2 Measure the width of a pulse by counting (up to 65,536) at a
rates from 600 kHz to 300 Hz.
3 Count negative-going edges for each two channels. The
maximum count for high-speed counting (5 kHz to 600 kHz)
is 65,536. For low speed counting, the maximum count not
limited by hardware.
Analog Output
One analog output (named DAC) is provided. The output can be
either a 0–10V (connect jumper J7:2-3) voltage output or a 0–20
mA current output (connect J7:1-2) suitable for driving 4–20
mA current loops. It will drive 20 mA up to 470 ohms. The
resolution is 10 bits.
259
U31
DAC8, U29
OUT
8
+
–
324
BIT[9-2] MSB
1640K
820K
3.9K
273
U24
8
D[0–7]
A[0–2]
D0
U27C
+
–
324
U27B
470K
470K
10K
100p
10
J7
Current
Voltage
DAC
10K
BITS
BIT[0]
LSB
BIT[1]
100p
An 8-bit DAC chip, a network of resistors, and LM324 op-amps
produce the output. Software writes the 10-bit output value to
three registers:
DAC UEXP Which bits
0x90 0x88 Bits 9–2
0
xA2 0xA0 Bit 1
0
xA3 0xA1 Bit 0
Another 10-bit analog output channel (UEXP) is available if it is
not used to provide reference voltage for the universal inputs. It
produces 0–10V with 10-bit resolution.
+
–
324
3.9K
U27A
100p
UEXP
259
U31
DAC8, U22
OUT
8
BIT[9-2] MSB
1640K
820K
273
U28
8
D[0–7]
A[0–2]
D0
BITS
BIT[0] LSB
BIT[1]
Note that UEXP is not identical to the first DAC channel.