External UART IC

[Terry]

I have a project where I need two UARTs operating simultaneously, so I need hardware UARTS with buffers. Since almost all the PIC chips only have one hardware UART I would like to add an external UART with either a SPI or I2C interface. Does anybody know of some UART IC's?
Terry

[Ron Marcus]

How much of a buffer do you need?

[Terry]

Minimum 2 bytes, since that is what I am use to with the PIC hardware UART, more is always better.
Terry

[Luciano]

Hi,


The MAX3110E/MAX3111E combine a full-featured universal asynchronous receiver/transmitter (UART) with ±15kV ESD-protected RS-232 transceivers and integrated charge-pump capacitors into a single 28-pin package for use in space-, cost-, and power-constrained applications. The MAX3110E/MAX3111E also feature an SPI™/QSPI™/MICROWIRE™-compatible serial interface to save additional board space and microcontroller (µC) I/O pins.
A proprietary low-dropout output stage enables the 2-driver/2-receiver interface to deliver true RS-232 performance down to VCC = +3V (+4.5V for MAX3110E) while consuming only 600µA. The receivers remain active in a hardware/software-invoked shutdown, allowing external devices to be monitored while consuming only 10µA. Each device is guaranteed to operate at up to 230kbps while maintaining true EIA/TIA-232 output voltage levels.

The MAX3110E/MAX3111E's UART includes a crystal oscillator and baud-rate generator with software-programmable divider ratios for all common baud rates from 300baud to 230kbaud. The UART features an 8-word-deep receive FIFO that minimizes processor overhead and provides a flexible interrupt with four maskable sources. Two control lines (one input and one output) are included for hardware handshaking.

The UART and RS-232 functions can be used together or independently since the two functions share only supply and ground connections (the MAX3110E/ MAX3111E are hardware- and software-compatible with the MAX3100 and MAX3222E).

MAX3110E/MAX3111E
http://www.maxim-ic.com/quick_view2.cfm?pdf_num=2052

MAX3110E/MAX3111E PDF datasheet:
http://pdfserv.maxim-ic.com/en/ds/MAX3110E-MAX3111E.pdf

Basic Stamp code for the MAX3110E UART:
http://www.wd5gnr.com/suart.htm

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The MAX3100 universal asynchronous receiver transmitter (UART) is the first UART specifically optimized for small microcontroller-based systems. Using an SPI™/Microwire™ interface for communication with the host microcontroller (µC), the MAX3100 comes in a compact 16-pin QSOP. The asynchronous I/O is suitable for use in RS-232, RS-485, IR, and opto-isolated data links. IR-link communication is easy with the MAX3100's infrared data association (IrDA) timing mode.
The MAX3100 includes a crystal oscillator and a baud-rate generator with software-programmable divider ratios for all common baud rates from 300 baud to 230k baud. A software- or hardware-invoked shutdown lowers quiescent current to 10µA, while allowing the MAX3100 to detect receiver activity.

An 8-word-deep first-in/first-out (FIFO) buffer minimizes processor overhead. This device also includes a flexible interrupt with four maskable sources, including address recognition on 9-bit networks. Two hardware-handshaking control lines are included (one input and one output).

The MAX3100 is available in 14-pin plastic DIP and small, 16-pin QSOP packages in the commercial and extended temperature ranges.


max3100
http://pdfserv.maxim-ic.com/en/ds/MAX3100.pdf

IrDA with the BASIC Stamp & the MAX3100
http://www.emesystems.com/BS2IrDA.htm


Best regards,

Luciano

[Ron Marcus]

Why not use a separate 18F 18 pin device as a slave? You'll have a huge amount of buffer space, and can use the MSSP module to make a 4 MHz hardware link to the master. (16 Meg clock)