Beeb816Mk2B Operation and Construction Notes
This is a respin of the MK2A board, mainly to replace the obsolete XC95108 CPLD with a more up to date XC95144XL part.
The newer CPLD has a 3V3 only core with 5V tolerant IO, so many changes have been made to accommodate the voltage change including the addition of an on-board regulator.
In normal operation the system VDD will be connected to the 3V3 regulator, ie the CPU, SRAM and CPLD core will all run on the same supply, with only the host and CPLD IOs on the 5V rail.
Link and PCB pins allow experiments with powering the CPU and SRAM with other voltages, mainly to test for latch-up issues with the CPLD rather than to gain any more speed from the processor subsystem.
The links are marked differently on the PCB from the slides above
| PCB Name | Slide Name | Instruction |
|---|---|---|
| CLKLNK | na | Make this link only if needing to add a LPF cap to the incoming clock signal |
| VDD_5V_LNK | L1 | Make this link to power the regulator from the 5V coming in from the host |
| SYSVDD_LNK | L2 | Link the left most 2 pins to select 3V3 for the CPLD/SRAM subsystem |
| Link the right most 2 pins to select 5V for the CPLD/SRAM subsystem |
NB for the SYSVDD_LNK/L2 the order of the pins in the simplified slide above is different to the order on the PCB. The table shows the correct setting for this link.
The following table is an example BOM from Digi-Key.
| Manufacturer Part Number | Manufacturer | Description | Digi-Key Part Number | Customer Reference | Reference Designator | Quantity | Unit Price | Extended Price | VAT | Subtotal |
|---|---|---|---|---|---|---|---|---|---|---|
| AS6C4008-55PCN | "Alliance Memory, Inc." | IC SRAM 4MBIT PARALLEL 32DIP | 1450-1027-ND | 512Kx8 SRAM | SRAM | 1 | 4.34000 | £4.34 | £0.87 | £5.21 |
| A 32-LC-TT | Assmann WSW Components | CONN IC DIP SOCKET 32POS TIN | AE10354-ND | 32pin DIL Socket | SRAM (Socket) | 1 | 0.34000 | £0.34 | £0.07 | £0.41 |
| PRPC040SAAN-RC | Sullins Connector Solutions | CONN HEADER VERT 40POS 2.54MM | S1011EC-40-ND | Pin strip for JTAG/GPIO pins | "JTAG and GPIO" | 1 | 0.48000 | £0.48 | £0.10 | £0.58 |
| A 40-LC-TT | Assmann WSW Components | CONN IC DIP SOCKET 40POS TIN | AE10008-ND | 40 pin DIP Socket for CPU | CPU (Socket) | 1 | 0.38000 | £0.38 | £0.08 | £0.46 |
| XG4A-4034 | Omron Electronics Inc-EMC Div | CONN HEADER R/A 40POS 2.54MM | OR893-ND | 40 pin PCB header (latching) | CON | 1 | 1.85000 | £1.85 | £0.37 | £2.22 |
| ADIP 40Z-LC | Assmann WSW Components | CONN DIP HDR IDC 40POS VERT | HDP40S-ND | 40 Pin DIL Header | None | 1 | 1.50000 | £1.50 | £0.30 | £1.80 |
| 1658621-9 | TE Connectivity AMP Connectors | CONN RCPT 40P IDC 26-28AWG GOLD | AKC40H-ND | 40 Pin IDC Female Connector | None | 1 | 1.50000 | £1.50 | £0.30 | £1.80 |
| 3365/40 300 | 3M | CBL RIBN 40COND 0.050 GRAY 1' | 3M157807-1-ND | Ribbon Cable | None | 1 | 1.39000 | £1.39 | £0.28 | £1.67 |
| 1107741 | Aries Electronics | OSCILLATOR SOCKET FULL SIZE 4PIN | A462-ND | Oscillator Socket | OSC (Socket) | 1 | 0.55000 | £0.55 | £0.11 | £0.66 |
| RNMF14FAD47K0 | Stackpole Electronics Inc | RES 47K OHM 1/4W 1% AXIAL | RNMF14FAD47K0CT-ND | RDY Pullup | R47K | 1 | 0.07000 | £0.07 | £0.01 | £0.08 |
| SR151A470KAR | AVX Corporation | CAP CER 47PF 100V C0G/NP0 RADIAL | 478-11006-ND | Clock filter Cap | C47PF | 1 | 0.34000 | £0.34 | £0.07 | £0.41 |
| ACO-12.000MHZ-EK | Abracon LLC | XTAL OSC XO 12.0000MHZ HCMOS TTL | 535-9205-5-ND | 12MHz oscillator | OSC | 1 | 1.52000 | £1.52 | £0.30 | £1.82 |
| C330C105K5R5TA | KEMET | CAP CER 1UF 50V X7R RADIAL | 399-4389-ND | Regulator capacitors | reg_cap* | 2 | 0.38000 | £0.76 | £0.15 | £0.91 |
| MCP1700-3302E/TO | Microchip Technology | IC REG LINEAR 3.3V 250MA TO92-3 | MCP1700-3302E/TO-ND | Regulator | REG3V3 | 1 | 0.28000 | £0.28 | £0.06 | £0.34 |
| CF14JT330R | Stackpole Electronics Inc | RES 330 OHM 1/4W 5% AXIAL | CF14JT330RCT-ND | Current Limiting Res. | r330* | 25 | 0.01920 | £0.48 | £0.10 | £0.58 |
| CF14JT10K0 | Stackpole Electronics Inc | RES 10K OHM 1/4W 5% AXIAL | CF14JT10K0CT-ND | "DIP0 | 1 Pull ups" | r10K* | 2 | 0.07000 | £0.14 | £0.03 |
| QPC02SXGN-RC | Sullins Connector Solutions | "CONN JUMPER SHORTING .100"" GOLD" | S9337-ND | Link headers | *lnk | 3 | 0.07000 | £0.21 | £0.04 | £0.25 |
| 206-2ST | CTS Electrocomponents | SWITCH SLIDE DIP SPST 50MA 24V | CT2062ST-ND | DIP 2 SW | dip | 1 | 0.66000 | £0.66 | £0.13 | £0.79 |
| XC95144XL-10TQG100C | Xilinx Inc. | IC CPLD 144MC 10NS 100TQFP | 122-1372-ND | XC95144XL CPLD | CPLD | 1 | 6.80000 | £6.80 | £1.36 | £8.16 |
| C322C104K5R5TA | KEMET | CAP CER 0.1UF 50V X7R RADIAL | 399-4329-ND | Decoupling Caps | c100n_* | 2 | 0.18000 | £0.36 | £0.07 | £0.43 |
| 08055C104KAT4A | AVX Corporation | CAP CER 0.1UF 50V X7R 0805 | 478-10836-1-ND | Decoupling SMD caps | c100n*smd | 3 | 0.07000 | £0.21 | £0.04 | £0.25 |
| USR1E220MDD1TP | Nichicon | CAP ALUM 22UF 20% 25V RADIAL | 493-16001-1-ND | Electrolytic Cap | c22u* | 2 | 0.20000 | £0.40 | £0.08 | £0.48 |
| Total | £24.56 | £4.91 | £29.47 |
Additionally you will need to source the following parts
- WDC 65C816 CPU in a 40 Pin DIL package
- Beeb816 Mk2B PCB
