Table of Contents
SBC V2-004
The SBC V2 is a Zilog Z80 processor board. It's a 100x160mm board that is capable of functioning both as a standalone SBC or as attached to the ECB bus.
Previously known as the N8VEM SBC, development began in 2006 wth V1 and is currently still in development.
Features
- 4Mhz+ Zilog Z80 CPU.
- Up to 512Kb paged SRAM.
- Up to 1Mb EPROM or 512Kb Flash ROM.
- Serial Interface.
- IDE interface.
- Real Time Clock.
- Onboard sound.
- Battery backup for RTC and SRAM via super capacitor.
- Standard ECB bus interface.
- +5V power connector for Single Board Computer operation.
- Reset button.
- Status LED.
- Switchable clock speed.
Pictures
Changes from SBC V2-003A
- Addition of speaker circuit.
- Add solder jumpers for bypassing DS1210.
- Move status LED to corner of board as per other ECB boards.
- Align serial connector pinout and functionality to SBC Z180 Mark IV
- Add max232 solder jumpers for TTL level output.
- Add onboard super capacitor.
- Incorporate ppide.
- Update to Kicad 5.
- Add jumper settings to silkscreen.
- Move reset switch to edge of board and remove reset jumper.
- Add jumpers to configure battery backup source.
- Add cpu clock divider to support MSX.
- Default to hard Kontron reset mode.
- Add User input button on UART Ring Indicator line (for recovery mode in ROMWBW)
- Elimination of flow control jumpers.
Software Support
ROMWBW BIOS featuring:
- CP/M / ZSDOS
- RAM & ROM disk support.
- ROM based BASIC, FORTH and Monitor.
- Prebuild disk images
ROMWBW Eurocard expansion board driver support:
- RAMFLOPPY
- VDU
- CVDU
- VGA3
- Zilog Peripherals
- USB FIFO
- Disk I/O
- 4PIO
- SCG
- DSKY
- DUAL SD CARD
- MF-PIC
Most recent Kicad files can be found here: https://github.com/b1ackmai1er/SBC-V2-004
Parts List
| Reference | # | Value | DIP8 | DIP14 | DIP16 | DIP20 | DIP32 | DIP40 | |
|---|---|---|---|---|---|---|---|---|---|
| C1,C3-C23,C29,C30,C32,C33 | 16 | 0.1uF | Ceramic Capacitor | ||||||
| C2 | 1 | 10uF | Electrolytic Capacitor | ||||||
| C31 | 1 | 22uF | Electrolytic Capacitor | ||||||
| C24-C27 | 4 | 1uF | Electrolytic or Tantalum Capacitor | ||||||
| C28 (REV V) | 1 | 10uF | Electrolytic Capacitor | ||||||
| C34 | 1 | 0.22F | Super Capacitor | ||||||
| D1 | 1 | 5mm LED | Red/Green Bicolor | ||||||
| D2 | 1 | 1N4148 | Diode | ||||||
| K1,K6-K13 | 9 | 1×3 | Pin Header 3 position 2.54mm | ||||||
| JP1, JP2, LS1,P6 | 4 | 1×2 | Pin Header 2 position 2.54mm | ||||||
| P1 | 1 | 2×20 | 40 pin IDC vertical socket. | ||||||
| P2 | 1 | 2.1mm | Barrel Jack Socket | ||||||
| P3 | 1 | 2×5 | 10 pin IDC vertical socket. | ||||||
| P4 | 1 | 4/8Mhz | CPU Clock 5V Active crystal oscillator square socket | 1 | |||||
| P5 | 1 | 1.8432Mhz | UART Clock 5V Active crystal oscillator square | ||||||
| Q1 | 1 | 2N3906 | PNP Transistor | ||||||
| SW1 | 1 | 6x6mm | Mini Push Button Switch DIP 4pin | ||||||
| R1 | 1 | 10R | 0.25w resistor | ||||||
| R2,R11 | 2 | 10K | 0.25w resistor | ||||||
| R9 | 1 | 100R | 0.25w resistor | ||||||
| R12 | 1 | 4K7 | 0.25w resistor | ||||||
| R13 | 1 | 3K6 | 0.25w resistor | ||||||
| R14 | 1 | 1K8 | 0.25w resistor | ||||||
| R15 | 1 | 120R | 0.25w resistor | ||||||
| R16 | 1 | 470R | 0.25w resistor | ||||||
| RR1 | 1 | 1K | SIP-6 Resistor array | ||||||
| RR2 | 1 | 4K7 | SIP-6 Resistor array | ||||||
| U1 | 1 | 16550 | UART DIP40 socket | 1 | |||||
| U2 | 1 | 27C080 | EPROM 512kb DIP32 socket | 1 | |||||
| U3 | 1 | 74LS08 | Quad 2-in AND Gate DIP14 socket | 1 | |||||
| U4 | 1 | 74LS10 | Triple 3-Input NAND Gate DIP14 socket | 1 | |||||
| U5 | 1 | 74LS125 | Tri State Quad Bus Buffer DIP14 socket | 1 | |||||
| U6 | 1 | 74LS139 | Dual 1-of-4 Decoder/De-multiplexer DIP16 socket | 1 | |||||
| U7,U27 | 2 | 74LS14 | Hex Inverter/Schmitt Trigger DIP14 socket | 2 | |||||
| U10 | 1 | 74LS243 | Quad Bus Transceiver DIP14 socket | 1 | |||||
| U8,U9,U11 | 3 | 74LS245 | Octal tri-state bus transceiver DIP20 socket | 3 | |||||
| U12,U13,U18 | 3 | 74LS174 | Hex D-type flip flop with clear DIP16 socket | 3 | |||||
| U14-U16 | 3 | 74LS32 | Quad 2-input OR gate DIP14 socket | 3 | |||||
| U17 | 1 | 74LS244 | Octal Driver Tri-State DIP20 socket | 1 | |||||
| U19 | 1 | 8255 | Programmable Peripheral Interface DIP40 socket | 1 | |||||
| U20 | 1 | C96ABC | DIN 41612 Connector, 96 pin plug, right angle. | ||||||
| U21 | 1 | DS1302 | Maxim Trickle-Charge Timekeeping Chip DIP8 socket | 1 | |||||
| U22 | 1 | MAX232 | Maxim Multichannel RS-232 Drivers/Receiver DIP16 socket | 1 | |||||
| U23 | 1 | AS6C4008 | 512Kb x 8 RAM or AS6C1008 128Kb x8 RAM DIP32 socket | 1 | |||||
| U24 | 1 | Z84C00 | Z80 CPU DIP40 socket | 1 | |||||
| U25 | 1 | DS1210 | Maxim Nonvolatile Controller Chip DIP8 socket | 1 | |||||
| U26 | 1 | 74LS06 | Hex inverter buffers/drivers DIP14 socket | 1 | |||||
| U28 (REV V) | 1 | 74LS74 | Dual D-Type Positive Edge Triggered Flip Flop DIP 14 socket | 1 | |||||
| X1 | 1 | 32.768KHz | 3mm Crystal 6pF | ||||||
| DIP Sockets | 3 | 11 | 5 | 4 | 2 | 3 |
Jumpers
Default setting with Super capacitor, DS1302 RTC, DS1210 Power Manager, 27C080 EPROM and AS6C4008 512Kb RAM Installed:
| JUMPER | DESCRIPTION | OPTIONS | DEFAULT | MEANING |
|---|---|---|---|---|
| JP1 | BATSEL | OPEN - CLOSED | OPEN | Disconnect RAM and RTC from ECB bus backup power. |
| JP2 | 1BIT-IN | OPEN - CLOSED | OPEN | Do not use ROMWBW console switch facility. |
| JP3-4 | RAMVCC, RAM CS | ALL OPEN - ALL CLOSED | ALL OPEN | DS1210 Installed. |
| JP5-8 | RXD, TXD, CTS, RTS | ALL OPEN - ALL CLOSED | ALL OPEN | MAX 232 installed. |
| JP9 | RECOVERY | OPEN / CLOSED | OPEN | Pin header to recovery mode button (version Z) |
| K1 | A17 | 1-2 / 2-3 | 1-2 | 27C080 EPROM Installed. |
| K6 | A18 | 1-2 / 2-3 | 1-2 | 27C080 EPROM Installed. |
| K7 | 128/512 | 1-2 / 2-3 | 1-2 | AS6C4008 512Kb RAM Installed. |
| K8 | A19 | 1-2 / 2-3 | 1-2 | 27C080 EPROM Installed. |
| K9 | PWR | 1-2 / 2-3 | 1-2 | Disconnect 5V from IDE connector. |
| K10 | BNKSEL | 1-2 / 2-3 | 1-2 | Select top of RAM to be fixed, bottom to be switchable. |
| K11 | 16K/32K | 1-2 / 2-3 | 1-2 | Select top fixed RAM size to be 32Kb. |
| K12 | INTSEL | 1-2 / 2-3 | 1-2 | Connect 16550 UART to interrupt line. |
| K13 | RSTSEL | 1-2 / 2-3 | 2-3 | Select KONTRON reset method. (Removed) |
Jumper Descriptions
| JUMPER | DESCRIPTION |
|---|---|
| JP1 | BATSEL - Battery Select |
Retention of memory and RTC time and data is supported on the SBC V2. The source of backup power to the memory and RTC is controlled by JP1. Power from the on-board super capacitor and/or from the ECB-BUS backup power line can be selected.
Closing JP1 will connect the ECB bus backup power in parallel with the onboard super capacitor. If JP1 is open then only the super capacitor will provide backup power. The DS1302 can be configured through software to provide charging power to the on board super capacitor and other power sources connect to the ECB bus backup power line. If the power source does not support charging i.e. battery then JP1 should be left open.
| JUMPER | DESCRIPTION |
|---|---|
| JP2 | 1BIT-IN - 1 Bit input |
Do not use ROMWBW console switch facility.
| JUMPER | DESCRIPTION |
|---|---|
| JP3 | RAMVCC - RAM 5 Voltage |
| JP4 | RAMCS - RAM Chip Select |
The DS1210 Power Manager provides controlled switchover to battery / supercapacitor on power down for the RAM and RTC to prevent corruption.
If the DS1210 is not installed then these solder jumpers should be bridged so that the CS and VCC power are connected to the RAM.
| JUMPER | DESCRIPTION |
|---|---|
| JP5 | RXD TTL solder bridge |
| JP6 | CTS TTL solder bridge |
| JP7 | TXD TTL solder bridge |
| JP8 | RTS TTL solder bridge |
Link all solder bridges for TTL level RS232 signals when MAX232 is not installed.
| JUMPER | DESCRIPTION |
|---|---|
| K1 | A17 - Address line 17 |
| K6 | A18 - Address line 18 |
| K7 | A19 - Address line 19 |
These three jumpers are used for configuring the type of EPROM or FLASH memory being used. See below for examples.
| JUMPER | DESCRIPTION |
|---|---|
| K7 | 128/512 - 128Kb or 512Kb RAM option. |
Selects the size the RAM chip installed by routing either VCC ( 5V) or address line 17 to pin 30 of RAM chip U23. ROMWBW defaults to 512Kb RAM. If 128Kb RAM is installed then a custom ROM image should be regenerated with the following option:
SBC_std_cust.asm:
RAMSIZE .SET 128 ; SIZE OF RAM IN KB, MUST MATCH YOUR HARDWARE!!!
Jumper 1-2 if an AS6C4008 512Kb RAM is installed or jumper 2-3 if a AS6C1008 128Kb RAM is installed.
| JUMPER | DESCRIPTION |
|---|---|
| K9 | PWR - Power to IDE connector option |
| JUMPER | DESCRIPTION |
|---|---|
| K10 | BNKSEL - Bank Selection option |
| JUMPER | DESCRIPTION |
|---|---|
| K11 | 16K/32K - 16K or 32K fixed RAM top option |
| JUMPER | DESCRIPTION |
|---|---|
| K12 | INTSEL - Interrupt select option |
| JUMPER | DESCRIPTION |
|---|---|
| K13 | RSTSEL - Reset select option. |
The Retrobrew ECB bus is based on a design called the Kontron bus,. Early Retrobrew ECB bus and board designs incorrectly implemented the RESET circuit design. This jumper allows the SBC V2 to be configured for the corrected design call KONTRON or the older design (LEGACY / N8VEM). All board in a system must use the same reset style. Most newer boards have an option to select either style but older boards are hardwired for LEGACY / N8VEM style reset.
Jumper 1-2 for LEGACY / N8VEM style reset or 2-3 for KONTRON style. Option removed in final version. Now hardwired for KONTRON mode.
Connectors
Resources
Version Z includes fix for clock divider pullup and widens power traces.
:boards:sbc:sbc_v2:sbc_v2-004:sbc-v2-004z-schematic.pdf
Version U.
:boards:sbc:sbc_v2:sbc_v2-004:sbc-v2-004v-schematic.pdf
:boards:sbc:sbc_v2:sbc_v2-004:sbc-v2-004v-board.pdf
:boards:sbc:sbc_v2:sbc_v2-004:sbc-v2-004v-gerbers.zip
:boards:sbc:sbc_v2:sbc_v2-004:sbc-v2-004v-kicad5.zip
Version Q designs have been manufactured and proven good. Version R corrects the silk screen errata.
Errata
Version U - Silkscreen mixed up for R1 and R2 resulting in reset button failing. R2 should be resistor closest to reset jumper and should be 10K. R1 is resistor closest to reset switch and should be 10R. Lots of silkscreen reverted to Fab layer somehow. Fixed in revision R
Version V - CPU oscillator may not work due to incorrectly placed pull up resistor. A 1k resistor needs to be added between pin 12 and pin 14 of U26 74LS06.
