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Amber Zeller 0b3f9f4703 add more detail to tech specs

2021-05-07 23:02:02 -04:00

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CHIBI PC-09 Technical Specification

5-17-21 Amber Zeller

Quick Specs

CPU

1, 1.5, 2 MHz Motorola 6809

Memory

64k SRAM on external card for optional MMU capability. Seperated into 2k blocks, numbered 0-31. Only 62k of memory is accessible, due to the I/O block.

I/O

2k block, position 30. Addresses EFFF-F7FE. Further subdivided into 128 devices of 16 addresses each.

Address Space Diagram

Address Range	Description
0000 - 07FF	Kernal Root Block
0800 - EFFE	Standard Memory Blocks
EFFF - F7FE	I/O Block
F7FF - FFFF	Vector Block

I/O Block Description

11 bits per block

128 devices are possible, though will likely never be used.

Bits	Description
0-6	Device selection
7-10	Address selection

Expansion Card Description

Byte 0 of every card should contain a descriptor. The structure of the descriptor is described in the following table.

Bits	Descriptor
0-2	Type

Type Descriptor Table

Type Descriptor	Description	Example
000	Block Storage	SD Card
001	ANSI I/O Stream	UART
010	ANSI Compatible Graphics Device	VGA64
011	Input Device	Keyboard
1xx	Other	Other

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