Signal Generatorsvoltage converter

Serial-to-Parallel Converter Schematic Circuit Diagram

This converter may help if just the serial port on a personal computer is free, whereas the printer needs a parallel (Centronics) port. It converts a serial 2400 baud signal into a parallel signal.

The TxD line, pin 3, CTS line, pin 8, and the DSR line, pin 6, of the serial port, are used — see diagram. The CTS and DSR signals enable handshaking to be implemented.

Serial-to-Parallel Converter Schematic Circuit DiagramSince the computer needs real RS232 levels, an adaptation from TTL to RS232 is provided in the converter by a MAX232. This is an integrated level converter that transforms the single +5 V supply into a symmetrical ±12 V one.

The serial-to-parallel conversion is affected by IC1. This is essentially a programmed PIC controller that produces a Centronics-compatible signal from a 2400 baud serial signal (eight data bits, no parity, one stop bit). The IC also generates the requisite control signals. If there is a delay on the Centronics port, the RS232 bitstream from the computer may be stopped via the Flow signal (pin 17). This ensures that no data is lost.
The controller needs a 4 MHz ceramic resonator, X1.

The MAX220   family of line drivers/receivers is intended for all EIA/TIA-232E and V.28/V.24 communications interfaces, particularly applications where ±12V is not available. The MAX225, MAX233, MAX235, and MAX245/MAX246/ MAX247 use no external components and are recommended for applications where printed circuit board space is critical. The MAX220-MAX249 are offered in 26 different packages
with temperatures from 0 to +70°C up to -55°C to +125°C. See the ordering information table at the end of the datasheet for all package and temperature options.

  • Meets or Exceeds TIA/EIA-232-F and ITU Recommendation V.28
  • Operates From a Single 5-V Power Supply With 1.0-µF Charge-Pump Capacitors
  • Operates up to 120 kbit/s
  • Two Drivers and Two Receivers
  • ±30-V Input Levels
  • Low Supply Current: 8 mA Typical
  • ESD Protection Exceeds JESD 22 – 2000-V Human-Body Model (A114-A)
  • Upgrade With Improved ESD (15-kV HBM) and 0.1-µF Charge-Pump Capacitors are Available With the MAX202 Device
  • TIA/EIA-232-F
  • Battery-Powered Systems
  • Terminals
  • Modems
  • Computers

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