Control Panel And Ce Lights; Sense Latches - IBM 5256-1 Maintenance Information Manual

CONTROL PANEL AND CE LIGHTS
The control panel circuit is the interface for operator
interaction with the printer. The microprocessor turns
indicators off and on, interprets switch settings, and
starts the correct reaction to switch changes.
Sense Latches
The sense latches store the status of the control panel
momentary contact switches and of the 'printer
mechanism ready' signal. The latches are set to zero
before each line is printed. The MPU reads the latch
status after each line is printed to determine if action is
required. The Start, Stop, Form Feed, and Line Feed
switches and the Cancel position of the Status switch
are all momentary contact switches and are therefore
stored in the latches. The Line Spacing switch and the
Test and Normal positions of the Status switch are not
Printer Adapter Data Flow
Planar
I
MPU and Storage
I
I
I
~~ntroller
(f
Cable
to-
I Read-only
to-
I
Adapter
Storage
I
I
(ROS, for
~--
__ ---.J
controls)
I
Micropro-
I
cessing Unit
I
I
I
I
Address
I
Decode
I
I/O Control
and
Register
I
2 Receive
Select
I
Buffers
I
2 Print
I
Buffers
1 - - - - - _ - _ . _ _ _
J
Timing
Circuits
•
momentary contact switches. However, the Status
switch positions are stored in latches. The Line Spacing
switch position is not stored in a latch. Latching is
required for the Status switch positions to determine if
the switch position was changed while a line was being
printed.
If 2 switches are sensed that cannot be serviced at the
same time, the switch that would cause the least activity
is serviced. For example, if the Form Feed and the Line
Feed switches were sensed at the same time, a line
feed would occur. The Stop switch always overrides
the Start switch if the 2 are sensed together.
The control panel lights are described in reference 193.
Printer Adapter
Printer
10
,.
Jumpers
Control
•
Panel
and CE
Lights
Control
Wire Fire Time
Print
Emitter
Control
I
Wire Fire Time
Sense
Latches
Printer
Input
Registers
and
Character
Generator
Forms
Control
Carrier
Motor
Control
Theory,
Features
~
Printer
Theory 5256 MIM 4-17