CHAPTER 2 CONTROLS AND INDICATORS
2.5 TELETYPE, MODEL 33 ASR
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IFigure 2-1. PDP-12 Operator console
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Table, 2-1. Central Processor Register Indicators Table 2-2. Central Processor Major State Indicators
Indicator Bits Indicator State
INST FIELD 5 F Instruction Fetch
DATA FIELD 5 D Deferred Address
RELAYS 6 E Instruction Execution
INSTRUCTION REGISTER 12 E2 Instruction Execution 2
PROGRAM COUNTER 12 INT Program Interrupt
MEMORY ADDRESS 12 WC Word Count
MULTIPLIER QUOTIENT 12 CA Current Address
ACCUMULATOR 12 B Break
LINK 1 TB Tape Break
MEMORY BUFFER 12
Table 2-3. Central Processor Miscellaneous Indicators
Indicators Interpretation When Lit
SKIP Skip Flip-Flop is set
FLO Overflow Flip-Flop is set
8MODE Processor is in the PDP-8 Mode
LINC MODE Processor is in the LINC Mode
RUN Processor is running
AUTO Auto Restart Flip-Flop is set
TRAP Trap flip-flop is set
INT PAUSE An internal pause is occurring
ION Program Interrupt facility enabled
I/O PAUSE An I/O Pause is occurring
Indicator IP XA
NP
MK TAPE INST
Table 2-4. Tape Processor Major State Indicators
Indicator State
I Idle
s
SearchB Block
c
Check WordT Tum Around
Table 2-5. Tape Processor Miscellaneous Indicators Interpretation
In Progress
Extended Address Mode
No Pause Mode
Mark Flip-Flop
3-bit Tape Instruction Register
Function
Indicates that a tape operation is In Progress.
Indicates that the processor is in the Extended Address mode.
Indicates that the processor is in the No Pause mode.
Indicates that the Mark Flip-Flop is set.
These three lights indicate the contents of the 3-bit Tape Instruction register.
Table 2-6. Function of Computer Console Keys
Key Function
1/0 PRESET This switch causes the processor to halt when it is in Internal Pause state during a tape instruction, and sets processor mode to the state of the console MODE switch. The Inst Field register is set to 2 and the Data Field register is set to 3. 1/0 PRESET pulse and the 1/0 BUS INITIALIZE pulse clear all 1/0 device flags and operations. The AC and Link are cleared.
DO This switch causes the processor to perform one instruction. In the LINC mode, the processor performs the instruction defined by the Left Switches (and the Right Switches, if it is a double word instruction). In the 8 mode, the processor performs the instruction defined by the Left Switches.
START 20 This switch causes the processor to start at location 20 of the currently selected Instruction Field.
START 400 This switch causes the processor to start at location 400 of the currently selected Instruction Field.
START LS This switch causes the processor to start at the 15-bit address specified by the Left Switches and the Instruction Field Switches.
CONT This switch causes the processor to resume operation.
EXAM The contents of the Left Switches are transferred into the Memory Address register. The contents of the absolute core address designated by the Left Switches are displayed in the Memory Buffer register.
STEP EXAM This switch increments the contents of the Memory Address register and displays the contents of this new address in the Memory Buffer register. This incrementing extends over 10 bits in LINC mode and 12 bits in 8 mode.
FILL The contents of the Left Switches are transferred into the Memory Address register. The contents of the Right Switches are deposited into the memory location whose absolute address is designated by the Left Switches and the Instruction Field switches.
FILL STEP Depressing this switch causes the contents of the Right Switches to be deposited into the memory location whose address is in the Memory Address register. Releasing this switch increments the contents of the Memory Address register. This incrementing extends over 10 bits in the LINC mode or 12 bits in the 8 mode. The Memory Buff er register then displays the contents of the location specified by the new contents of the Memory Address register.
MODE This switch determines the mode (LINC or 8) to which the processor will be set when the 1/0 PRESET switch is activated. The MODE switch is effective only when the computer is not running.
Key
AUTO
Table 2-6. Function of Computer Console Keys (cont) Function
This switch sets the AUTO RESTART flip-flop if it is held down at the same time one of the following keys is actuated: STEP EXAM, FILL STEP, DO, or CONT.
The AUTO RESTART flip-flop causes the central processor to start automatically at the end of a variable time delay· (determined by the console controls) after the central processor stops for any of the following reasons:
a. SING STEP switch activated b. FETCH STOP address match c. EXEC STOP address match
d. The end of a STEP EXAM operation e. The end of a FILL STEP operation f. The end of a DO switch operation
The Auto Restart Flip-Flop is cleared by any of the following conditions:
a. STOP switch pressed while processor is running
b. DO, FILL STEP, or STEP EXAM switch activated and the AUTO switch not pressed
c. A processor HLT instruction executed (either mode) d. I/O PRESET pulse is generated
To start a program in AUTO RESTART mode:
a. Start the program with the SING STEP switch up.
With the AUTO key depressed, depress CONT.
Register LEFT SWITCHES
RIGHT SWITCHES
INST FIELD
SENSE SWITCHES
Switch STOP
SING STEP
FETCH STOP
Table 2-7. Toggle Switch Registers
Bits 12
12
3
6
Function
These switches form a 12-bit word which can be read into the accumulator with the LINC mode instruction LSW (517). This word also specifies the address to be examined when the EXAM switch is used, the address into which data will be placed when the FILL switch is used, the stopping address for EXEC STOP and FETCH STOP functions, and the instruction to be performed when the DO switch is used.
The contents of these switches form a 12-bit word which can be read into the accumulator with the LINC mode instruction RSW (516) or the 8 mode instruction OSR (7 404 ). This word also provides data to be stored in memory when the FILL or FILL STEP switches are used. When the DO switch is used, the Right Switches contain the second word of two-word instructions.
These are a high-order extension of the Left Switches. They provide addressing information for systems equipped with 8K or more of memory for the EXAM, FILL, ST ART LS, EXEC STOP, and FETCH STOP functions.
These switches are individually interrogated by LINC mode skip instructions, thereby enabling console control of program branching.
Table 2-8. Individual Console Toggle Switches
Function
This switch causes the processor to stop at the end of an instruction. For the purposes of the STOP switch, Traps, Interrupt, Tape Break, and single-cycle Data Break are considered to be single-cycle instructions. During a three-cycle Data Break, the processor is stopped after the Break cycle.
This switch causes the RUN flip-flop to be cleared, thereby disabling the timing circuits at the end of one cycle of operation. Thereafter, repeated operation of the CONT switch steps the program one cycle at a time so that the operator can observe the contents of registers in each major state.
This switch causes the processor to stop when the address designated by the Left Switches matches the current address in the Memory Address register during the Fetch cycle. For systems with more than 4K of memory, the Inst Field switches designate the three most significant bits of the address.
Table 2-8. Individual Console Toggle Switches (cont)
Switch Function
EXEC STOP This switch causes the processor to stop when the address designated by the Left Switches matches the current address in the Memory Address register during any computer cycle except a Fetch cycle. For systems having more than 4K of memory, the Inst Field switches designate the three most significant bi ts of the address.
Figure 2-2. Analog Knobs and Power Switch Panel
Panel Controls OFF /ON/LOCK
SPEAKER VOLUME
AUTO RESTART DELAY
COARSE and FINE
ANALOG CHANNELS 0-7 (knobs)
Terminals
ANALOG CHANNELS 10-1 7 (Input Jacks)
RELAY REGISTER Contacts
EXTENSION SCOPE
Table 2-9. Analog Knobs and Power Switch Panel
Function
This 3-position, key-locking switch is used to turn the PDP-12 on as well as inhibit console intervention during an operating program. When fully counterclockwise, the PDP-12 is off. When turned to the center position, the PDP-12 is turned on and the console activated. When the switch is fully clockwise, the PDP-12 is on, but console control functions are totally inhibited while the PDP-12 RUN light is on. Only the Left Switches, Right Switches, and Sense Switches remain operative.
The volume of the speaker is controlled by this knob. (The speaker, which is driven by AC bit 0, is added to the system when the AD 12 is included in the system configuration.)
These two knobs control the delay period of Auto Restart after a processor stop due to an EXEC STOP, FETCH STOP, or SING STEP operation. (See AUTO switch description in Table 2-6.)
The COARSE delay selects overlapping ranges from 2.4 µs to .38 sec. The FINE control gives variation within a range of 20: 1 of the selected COARSE delay.
These 10-turn potentiometers are connected to analog input channels 0-7 of the ADI 2 Analog-to-Digital Converter. These knobs therefore provide eight continually-variable parameters within the range of ±5121 0 for program usage.
Table 2-10. Relay and Analog Input Panel Function
These are 3-conductor phone jacks providing ± 1 Volt input connections for AD 12 Analog-to-Digital converter channels 108 -17 8 •
One set of form C contacts for each of the six system relays is available at the binding posts.
A 24-pin connector for an extension scope provides for remote operations, multiple displays, or photographing of display output. See Appendix G for pin connections and drive characteristics.
Figure 2-3. Relay and Analog Input Panel
Figure 2-4. Type YR 12 CRT Display
Table 2-11. YR 12 Display Scope Controls
Control Function
CHANNEL Selects one or both channels for scope display.
BRIGHTNESS Controls level of brightness.
X GAIN Controls horizontal size of display.
X POS Controls horizontal position of display.
Y GAIN Controls vertical size of display.
Y POS Controls vertical position of display.
Figure 2-5. TUSS Tape Transport Control Panel
Table 2-12. TU55 Tape Transport Controls and Indicators
Control or Indicator Forward Tape-motion Switch (designated in Figure 2-5 by arrow pointing to the left)
WRITE ENABLED/WRITE LOCK switch WRITE ENABLED
WRITE LOCK
WRITE ENABLED
Unit Selector 0 1 2 3 4 5 6 7 OFF LINE
REMOTE/OFF /LOCAL Switch REMOTE
OFF
Function
Provides forward tape motion (i.e., from right to left) only if REMOTE/OFF /LOCAL switch is set to LOCAL.
Permits TCl 2 control system to write information on the TUSS.
Prevents writing. If TCl 2 control system is commanded to write on tape while the WRITE LOCK is set, the control signals a TAPE NOT OK.
Lights when WRITE ENABLE/WRITE LOCK switch is in the WRITE ENABLE position.
When this selector is dialed to one of the numerals and the REMOTE/OFF /LOCAL switch is set to REMOTE, the central processor may gain access to the unit.
When the selector is dialed to OFF LINE, the transport cannot be selected by the tape control.
NOTE
Some earlier units were equipped with a unit selector position 8, which is the same as unit 0.
Perrni ts tape processor to control the transport.
. Removes power from reel motors and releases the brakes. This permits the operator to change the tape.
Table 2-12. TU55 Tape Transport Controls and Indicators (cont)
Control or Indicator
LOCAL
REMOTE Indicator
Reverse Tape-motion Switch (designated in Figure 2-5 by arrow pointing to the right)
Function
Permits the forward and reverse tape-motion switches to provide tape motion in direction of the arrows. The transport cannot be selected.
Lights only when transport is selected by the tape processor.
Provides for motion in the reverse direction (i.e., from left to right), but only when REMOTE/OFF/
LOCAL switch is on LOCAL. If both reverse and forward tape-motion switches are pressed simulta-neously, reverse motion takes place.
Figure 2-6. Teletype Model 33 ASR
Table 2-13. Teletype Model 33 ASR Controls Control
Punch Controls REL Pushbutton B SP Pushbutton
ON and OFF Pushbuttons
Reader Control
ST ART /STOP /FREE
LINE/OFF /LOCAL Switch
Function
Disengages the tape in the punch to allow removal or loading.
Backspaces the tape in the punch one space, allowing manual correction or rubout of the character just punched.
ON engages the punch for operation under local or program control. OFF removes the punch from control.
In the FREE (lowest) position, the tape feed wheel is disengaged, and tape can be loaded or unloaded.
In the STOP (center) position, the wheel is engaged but the reader cannot be operated. In the START (highest) position, the reader can be operated under local or program control.
In the LINE position, the Teletype is energized and connected as an I/O device to the computer. In the OFF position, the Teletype is not energized. In the LOCAL position, the Teletype is energized for off-line operation, and signal connections to the processor are disconnected. Both LINE and LOCAL use of the Teletype require that the computer OFF/ON/LOCK switch is ON.
3.1 ORGANIZATION OF MEMORY