IBM 1 Series - Signal Line Considerations; Application Sequences; Interval Timer

Signal Line Considerations
Timer X Customer Clock
Timer X External Gate
Timer X Run State
Timer X External Gate Enable
Application Sequences
Interval Timer
The timer attachment digital outputs are solid state switches that can be
used with or without a customer source voltage. See “‘Drivers’’ in this
chapter.
The timer attachment digital inputs are TTL-compatible, and a
jumper-wire option is available on the card to provide a filter for these
inputs, if required in a noisy environment. A loss of frequency response is
the result of using the optional filter. Without filtering, the input rate can
go up to 1 MHz. With filtering, the input rate drops to 50 kHz, worst
case. For additional information, see ‘Jumper Selections’’ in this chapter.
“Timer X customer clock’ is the input for the user-supplied clock or for a
random pulse train. This input uses the down level, and not the down
transition, as active.
‘Timer X external gate’ is the input for the user-supplied gate signal. It is
only effective when the external gate control is enabled. This input uses
the down level, and not the down transition, as active.
‘Timer X run state’ is an output signal that indicates that the timer is in
the run state. Its primary purpose is for state synchronization of the timer
X external gate cycle. This signal becomes active with a Start Timer
command and remains active until a Stop Timer command is accepted, the
‘timer X external gate’ signal becomes inactive, or a halt/reset occurs.
‘Timer X external gate enable’ is an output signal that indicates that the
external gate has been enabled through bit 15 of the Set Timer Mode
command.
Perform the following steps to use the timer as an interval timer with an
external time base (customer clock input):
1. Prepare timer.
2. Set timer period and initial value.
3. Set timer mode (external time base—bit 14 of the IDCB data word set
to 1).
4. Start timer periodic.
The timer starts counting clock pulses and interrupts when the counter
underflows.
Timer Feature 3-7