Control Data Corporation INFORMATION SYSTEMS TERMINAL II Hardware Maintenance Manual page 90

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• 2K 8-bit words of ROM/EROM for terminal diagnostic
and loader program
• Timing generation for the display, memory, and con-
troller board
• Composite video output for external devices
Memory Expansion
The memory expansion consists of 16K 8-bit words. The
module consists of 8 ICs which are to be plugged into the
Video PCB. The board already has all the sockets to accept
the ICs and support logic to integrate them into the ter-
minal. Switch S2-l0 on the Controller Board must be placed
in the Off position (open).
Programming
All functions and capabilities of the terminal are con-
trolled by a program residing in memory and executed by a
Z80 microprocessor LSI chip. State time is set at 250
nanoseconds. The following paragraphs discuss the memory
structure.
Memory Structure
Figure 4-17 shows the memory breakdown and addressing. The
following paragraphs discuss:
• Read-Only Memory • Bulk Write/Erase
• Program RAM • Read Upper ID
• Display Refresh Memory
• Load Interrupt Mask
• Control of Peripherals • Read Serial Data
• I/O Peripheral Devices • Miscellaneous Control
• ~ead Configuration Switches • Read Serial Status
• Load Maintenance Register
• Load Serial Data
• Read Keyboard Data • Read Controller Status
• Load Transmitter Lower Bits
• Load Serial Control
• Read Touchpanel Data • Read Communication Line
• Load Transmitter Upper Bits
• Input Parallel Channel
• Read Lower ID
• Output Parallel Channel
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