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A Tour of the Hardware
| Part# | Integrated Circuit |
|---|---|
| U1 | Motorola MC68B09 or Hitachi HD63C09E MPU |
| U2 | Texas Instruments SN74HCT273N Octal Flip-Flop with Reset |
| U3 | Alliance AS6C4008-55PCN 4Mbit / 512KB SRAM |
| U4 | Motorola MC68B50 or Hitachi HD63B50 ACIA |
| U5 | Dallas Semiconductor DS1813 EconoReset |
| U6 | Phillips 74HCT02N Quad 2-Input NOR |
| U7 | Dallas Semiconductor DS1210 Nonvolatile Controller |
| U8 | Shenzhen Honglifa HLF SN74HCT139N Dual 2-to-4 Line Decoder / Demultiplexer |
| U9 | Atmel At28C256 256Kbit / 32KB Parallel EEPROM |
| U10 | Motorola MC74HCT138AN 3-to-8 Line Decoder / Demultiplexer |
| U11 | Dallas Semiconductor DS1233 EconoReset |
| U12 | - not present - |
| U13 | Phillips 74HCT20N Dual 4-input NAND |
Microprocessor Options
MC68B09
Microprocessor Option 1: Motorola's famous 8-bit microprocessor, the 6809.
The MC68B09 maximum clock is 2.0MHz without overclocking.
For simplicity and to reduce part counts, the SST-6809 uses the internally-clocked version of the MC6809, rather than the externally clocked MC6809E
Link to Data Sheet
HD63C09
Microprocessor Option 2: Hitachi's upgraded 8-bit microprocessor based on the Motorola 6809.
The Hitachi MPU sips less power, runs cooler, and contains additional registers and instructions capable of running with fewer clock cycles per instruction.
The HD63C09 maximum clock rate is 3.0MHz without overclocking.
Link to Data Sheet
Bus Routing
Full Address and Data bus lines (with most Control lines) route to the M8 bus connector, onboard memory, ACIA, and address decode circuitry.
SN74HCT273N
Memory paging latch.
AS6C4008-55PCN
Alliance Semiconductor 4Mib / 512KiB static RAM.
This RAM is capable of being battery backed up with the design of the SST-6809 board design and works with or without battery power.
MC68B50
Motorola's Asynchronous Communications Interface Adapter (ACIA) for serial communication.
HD63B50
Hitachi's upgraded Asynchronous Communications Interface Adapter (ACIA) based on the Motorola 6850.
DS1813
One of three reset circuit options for the SST-6809.
The DS1813 is the preferred or default option.
74HCT02N
Address decoding.
DS1210
Battery backup.
SN74HCT139N
Address decoding.
At28C256
32KiB EEPROM.
MC74HCT138AN
Address decoding.
DS1233
Reset circuit option.
There are three reset options, this is one.
74HCT20N
Address decoding.
Return to SST-6809