IBM 1 Series - Chapter 5. Integrated Digital Input;Output Feature; Introduction; Digital Input (DI)

Introduction
Digital Input (DI)
Chapter 5. Integrated Digital Input/Output Feature
The integrated digital I/O nonisolated feature allows the user to add
digital sensor I/O or non-IBM devices. This feature has the following
general characteristics:
e Two 16-point groups of nonisolated digital input/process interrupt
(DI/PI).
e Two 16-point groups of nonisolated digital output (DO).
e Four device addresses, one for each DI/PI or DO group. All four
devices prepared for interrupts with one Prepare command.
e External synchronization for each group of DI and DO. This
user-attachment feature permits asynchronous data transfers.
e Interrupts can be initiated by an external sync input (one input for
each DI or DO group) or by a O-to-1 transition on a PI point.
e The feature is contained on one logic card and can be plugged into
either the processor unit or the IBM 4959 I/O Expansion Unit.
Figure 5-1 is a simplified data flow of the integrated digital I/O feature.
The integrated digital I/O feature has two groups of digital input/process
interrupt. Each group of digital input has:
e User-input points (16) that sense the value of nonisolated voltage
input.
e One 16-position DI data register for reading unlatched data.
« One 16-position PI data register for reading latched data.
e An ‘external sync’ input line and a ‘ready’ output line.
e Interrupt capability from either external sync or process interrupt.
Each digital input group has a unique device address and responds to
specific commands. A description of addressing and commands can be
found in the IBM Series/1 processor description manual. Refer to the
Preface of this manual for the titles and order numbers. The data registers
and the functions performed by DI/PI are described in this section.
Each position of the DI data register follows the state of the corresponding
user-input point until the register is read. The data in the register is held,
either during a Read command or when the ‘external sync’ input becomes
active while in external sync mode. In the second case, the data remains
held until the resulting interrupt is serviced and the ‘ready’ line is
activated. For additional information, see ““DI External Sync”’ in this
‘section.
Integrated Digital Input/Output Feature 5-1