TS-2050 Modem Compatible Serial I/F

In response to Don’s request on page 6 of ZXir QLive to unscramble the schematic in the final issue of UPDATE! magazine. I had already done that – it was a challenge and I recognized the problem. Attached is the unscrabled version. The problem is one of proportional versus non-proportional fonts.

For example from page 6:

Courier font (non-proportional)

       ________________
      |      317       |
 +    |                |                 +
______| Vin       Vout |-----------------
      |                |      |       |
      |                |      |       |
      |______Adj_______|    [330]    ---
              |               |      ---
              |               |       |

Helvetica font (porportional) – figure above copied and then font changed.

        ______________
        |  317   |
         |        |
 +       |        |               +
_________| Vin     Vout|--------------
      |        |   |   |
      |        |   |   |
      |        |   |   |
      |______Adj_____|  [330]  ---
         |        |    ---
         |        |    |

I verified the pinout of the 8251 and corrected pin 24 callout to DTR.

Les Cottrell

TS2050 MODEM COMPATIBLE SERIAL I/F - schematic: 74HC138 address decoder (A5, A6, A7, A3, IORQ, M1; Y3 to 8251 CS), 8251 USART (D0-D7, RD, WR, C/D from A2, CLK, RST from RESET via 74HC14, DTR 24 not used), 74HC4060 with 10M and 4.912 MHz XTAL and 33 pF capacitors providing TXC/RXC via switch S1, 74HC14 line drivers/receivers with 100 ohm, 10K and 1M resistors to DB25/DB9 connector pins TX, RX, GND, RTS, CTS, DSR; 10 uF supply decoupling. "S1 for BAUD rate selection Q4=9600/1200 Q8=1200/300". "untangled" page 21 of final issue of Update! magazine
TS2050 MODEM COMPATIBLE SERIAL I/F – schematic: 74HC138 address decoder (A5, A6, A7, A3, IORQ, M1; Y3 to 8251 CS), 8251 USART (D0-D7, RD, WR, C/D from A2, CLK, RST from RESET via 74HC14, DTR 24 not used), 74HC4060 with 10M and 4.912 MHz XTAL and 33 pF capacitors providing TXC/RXC via switch S1, 74HC14 line drivers/receivers with 100 ohm, 10K and 1M resistors to DB25/DB9 connector pins TX, RX, GND, RTS, CTS, DSR; 10 uF supply decoupling. "S1 for BAUD rate selection Q4=9600/1200 Q8=1200/300". "untangled" page 21 of final issue of Update! magazine