IBM Series 1 User Manual page 117

TlftER FEATURE ELECTRICAL CHARACTERISTICS
Figure 3-2 shows the driver/receiver circuits.
Receivers
• The timer inputs jumpered for TTL input meet the
following specifications:
Input voltage:
Up
level:
Down level:
Input impedance:
+5.5 volts maximum
+2.4 volts minimum
+0.6 volts maximum
m
40 mA
0.0 volts minimum
~100
ohms
The input rate must be 1 MHz or less. The input should
be on for at least
300
nanoseconds and off for at least
300 nanoseconds at
any
input rate.
• The timer inputs jumpered for filtered TTL input meet
the following specifications:
Input impedance:
Input limits:
Logic one:
Logic zero:
Maximum
repetion rate:
~9.2
kilohms at less than 4.5V
~2 kilohms at +24V
+24
Vdc
maximum
-24 Vde minimum
51.0 ide
~2.5 Vdc
50 kHz worst case with 50% duty
cycle
worst case condition is an open collector driver. If
an active collector driver is used to drive the input
points, the maximum repetition rate will increase
substantially to approach 500 kHz. This is determined
by
the charging time of the filter shown in the
receiver circuit in Figure 3-2.
Each input point has an internal pull-up resistor,
regardless of whether the input is jumpered for
filtered or non-filtered input. Unconnected inputs are
held at the inactive state (up level).
3-10 GA34-0033
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