IBM 1 Series - Timer Feature Electrical Characteristics

Timer Feature Electrical Characteristics
Refer to Figure 3-2 for the driver/receiver circuits.
Receivers. The timer inputs jumpered for TTL input meet the following
specifications:
Input voltage:
Up level: +5.5 volts, maximum; +2.4 volts, minimum
Down level: +0.6 volt at 40 mA, maximum; 0.0 volt, minimum
Input impedance: >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: >9.2 kilohms at less than 4.5 V;
>2 kilohms at +24 V
Input limits: +24 Vdc, maximum; —24 Vdc, minimum
Logical 1: <1.0 Vde
Logical 0: >2.5 Vdc
Maximum
repetition rate: 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
increases 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 nonfiltered input. Unconnected inputs are
held at the inactive state (up level).
Drivers. The timer outputs meet the following specifications:
Output voltage:
1. With user source:
Off state: +52.8 Vdc, maximum
On state: +0.8 Vdc, maximum
2. Without user source:
Off state: +5.5 Vdc at 0.0 mA source, maximum;
+2.4 Vdc at 1.0 mA source, minimum
On state: +0.8 Vdc, maximum
Current input:
On state: 100 mA per point with user source, maximum
Off state: 500 wA per point at +52.8 Vdc
user source, maximum
Because the performance of this interface may be affected by noise,
appropriate arc suppression, noise filtering, etc., may be necessary on the
user’s inputs.
3-10 GA34-0033