1. The KC-85 and the U880 Team members: Nadine Spörl Angela Roggan Martin Burkard Alexander Becker

2. Kompakt Computersystem KC 85 series 1984-1990 in the GDR KC 85/1 (Z9001) Keyboard computer Basic Module Interpreter KC 85/2 (HC 900) Can use different OS KC 85/3 BASIC as programming language in ROM KC 85/4 1 basic device Improvement Graphic Sound Can be extended 2 module slots Separate keyboard

3. Upgrade the system plug in modules further interfaces Parallel ports Serial ports RAM ROM Operating System CAOS (Cassette Aided Operating System ) Loading/storing data via tape recorder interface Add - on devices Bus driver: extends the number of module slots by 4 Floppy disc expansion : a second U880 system access to up to 4 floppy disc drives IDE interface

4. 8 - bit (16-bit) load instruction Stack instruction Exchange instruction Block look - up and transfer instruction 8-bit (16-bit) arithmetic instruction Branch and subroutine instruction Rotation and shift instruction Instruction set

5. Registers Name B,C,D,E,H,L,W,Z P (or F) R I IX,IY PC SP Type general purpose registers Processor Status register Memory Refresh register Interrupt Page address registerindex registers Program Counter register Stack Pointer register Size 8-bit 16-bit

6. The internal organization of the U880

7. Flags Abbreviation N V 1 B D I Z C Type Negative flag Parity/Overflow flag UNUSED flag Break flag Decimal Node flag Interrupt Disable flag Zero flag Carry flag Location bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

8. Interrupts IRQ (maskable hardware interrupts) NMI (non-maskable hardware interrupt) BRK (software interrupt)

9. Addressing Modes nine different addressing modes –Immediate addressing (8-bit) –Immediate extending addressing (16-bit) –Relative addressing (8-bit) –Extended addressing (16-bit) –Indexed addressing (16-bit + 8-bit) –Register addressing (8-bit) –Register indirect addressing (16-bit) –Bit addressing –Modified page 0 addressing

10. Addressing Modes Immediate addressing (8-bit) 1.The Instruction Register is loaded with the opcode 2.The KC85 is incremented 3.The data byte, which is pointed at, is read into the U880 CPU 4.The instruction is executed 5. The result is stored in the accumulator 6.The KC85 is incremented and the next instruction is loaded

11. Addressing Modes Immediate extending addressing –used to load 16-bit registers –instructions therefore have two data bytes –most-significant data bit is read first –stored in the most significant bit of the target register –KC85 is incremented and these steps are repeated with the least-significant bit

12. Addressing Modes nine different addressing modes –Immediate addressing (8-bit) –Immediate extending addressing (16-bit) –Relative addressing (8-bit) –Extended addressing (16-bit) –Indexed addressing (16-bit + 8-bit) –Register addressing (8-bit) –Register indirect addressing (16-bit) –Bit addressing –Modified page 0 addressing

13. Perspective/Role on the Market Characteristics of the U880/Z80: a mid-seventies chip only eight bit very slow for today's standards

14. Perspective/Role on the Market Attractiveness: very cheap easy to handle for programmers and hardware designers 8bit exactly match the bus width of the vast majority of memories and peripherals on the market the chips architecture allows easy integration with on chip peripherals Tools are widely spread