F8

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F8 is a processor system which is used in the Fairchild Video Entertainment System (Channel F) and other machines (VideoBrain is worth mentioning). The smallest usable system usually contains a Central Processing Unit (CPU) 3850 and a Program Storage Unit (PSU) 3851 with 1kB space.
The 3850 is an 8-bit processor with 64 bytes of on-chip RAM and the first PSUs could generally hold 1kB of ROM data. To keep the chip pin count down the F8 system doesn't have an address bus but instead each chip in the system has it's own program counter. Control signals are sent to all chips in the system using five ROMC signals. Very innovative for its time.

Chips are listed below:

3850 CPU

Central Processing Unit
Arithmetic Unit
Accumulator
64 Byte scratchpad
Interrupt Logic
Two I/O-ports
Max 1 in System

3851 PSU

Program Storage Unit
1kB ROM
Control Bus 5 Lines
Program Counter
Stack Register
1 Data Counter
Timer
Interrupt Logic
Two I/O-ports
Max 63 in System

3852 DMI

Dynamic Memory Interface
Control Bus 5 Lines
Program Counter
Stack Register
2 Data Counters
16 Line Address Bus
Max 1 in System

3853 SMI

Static Memory Interface
Control Bus 5 Lines
Program Counter
Stack Register
2 Data Counters
16 Line Address Bus
Max 1 in System

3854 DMA

Direct Memory Access Controller
16 Line Address Bus
Max 4 in System

3856 PSU

2kB Program Storage Unit
Control Bus 5 Lines
Program Counter
Stack Register
2 Data Counters
Timer
Interrupt Logic
Two I/O-ports
Max 31 in System

3857 SMI/PSU

2kB Static Memory Interface and
Program Storage Unit
Control Bus 5 Lines
Program Counter
Stack Register
2 Data Counters
16 Line Address Bus
Timer
Interrupt Logic
Max 1 in System

3859

3850 + 3851

3861 PIO

Peripheral Input/Output
Two I/O-ports
Max 62 in System

3870

Single chip Microcomputer
Basically 3850 + 3856
Four I/O-Ports (0,1,4,5)
64 Byte Scratchpad RAM

3871 PIO

Peripheral Input/Output
Two I/O-ports
Max 62 in System

3872

Single chip Microcomputer
Basically 3850 + 3851
Four I/O-Ports (0,1,4,5)
1, 2, 3 or 4kB ROM
64 Byte Scratchpad RAM
64 Byte RAM
Same Pinout as 3870

3899 PSU

Program Storage Unit only
1kB ROM
No timer nor interrupt
Max 63 in System


Read more

Read more in F8_User's_Guide_(1976)(Fairchild) (.pdf 13.8MB)
Fairchild Microcomputers (.pdf 780kB)

External Links

http://www.nyx.net/~lturner/public_html/Fairchild_F8.html