The MK14E Backplane is a simple 3-slot design which follows the connections on the original MK14 VDU, sockets are on a 1" (25.4mm) pitch.
One important thing to note with regards to the MK14E backplane is that it is not compatible with the Acorn System Backplane.
Not only does the Acorn Backplane have both A32 and B32 joined together (0V) but 0V and +5V are swapped which would be catastrophic !
| Pin No. | Side A | Description | Side B | Description |
| 1 | 0V | Power 0V | +5V | Power +5V |
| 2 | A0 | Lower 12 bits of Address Bus from processor | +5V | |
| 3 | A1 | +5V | ||
| 4 | A2 | 0V | Power 0V | |
| 5 | A3 | 0V | ||
| 6 | A4 | 0V | ||
| 7 | A5 | EXT I/O | Pulling this line disables Mainboard memory and I/O | |
| 8 | A6 | NADS | Address Strobe, when low indicates status and upper four address lines are on data bus | |
| 9 | A7 | PB6 | 8154 (IC4) Port B | |
| 10 | A8 | PB5 | ||
| 11 | A9 | PB7 | ||
| 12 | A10 | PB4 | ||
| 13 | A11 | PB3 | ||
| 14 | A12 | Upper four Address lines from Latch IC3 | PB2 | |
| 15 | A13 | PB1 | ||
| 16 | A14 | PB0 | ||
| 17 | A15 | PA7 | 8154 (IC4) Port A | |
| 18 | D0 | Data Bus | INTR | |
| 19 | D1 | PA6 | 8154 (IC4) Port A | |
| 20 | D2 | PA0 | ||
| 21 | D3 | PA5 | ||
| 22 | D4 | PA1 | ||
| 23 | D5 | PA4 | ||
| 24 | D6 | PA2 | ||
| 25 | D7 | PA3 | ||
| 26 | NRST | System Reset (active low) | SENSEA | Sense A condition input to processor can also be used as interupt input |
| 27 | XOUT | Processor Xtal oscillator output (4MHz) | SIN | Serial Input to processor E-register |
| 28 | NRDS | Read Data Strobe, data read on trailing edge | SENSEB | Sense B condition input to processor, |
| 29 | NWDS | Write Data Strobe, when low indicates valid data on bus | SOUT | Serial Output from processor E-register |
| 30 | NENOUT | High when processor is using the bus | FLAG0 | Flag 0 output from processor |
| 31 | NENIN | Enable Input, when low processor can access bus | FLAG2 | Flag 2 output from processor |
| 32 | +5V | Power +5V | FLAG1 | Flag 1 output from processor |
Schematic
Bill Of Materials
Blank PCB
