PC87373 Datasheet, PDF (130/174 Pages) National Semiconductor (TI) – LPC SuperI/O with Glue Functions

11.0 Musical Instrument Digital Interface (MIDI) Port
11.1 OVERVIEW
This chapter describes a generic MIDI Port. For the implementation used in this device, see Section 3.17.1 on page 71.
The MIDI Port is an asynchronous receiver/transmitter that uses a two-wire, bidirectional, relatively slow communication
channel to transmit and receive data bytes to or from MIDI-compliant devices, according to a predefined communication pro-
tocol. The MIDI Port is compatible with MPU-401 UART mode.
The MIDI was originally defined to establish a standard interface between computers and digital musical instruments such
as synthesizers, and has become the de facto standard for this purpose. However, the MIDI is also commonly used for other
purposes, such as communicating with advanced game devices.
The MIDI Port serves as a communication pipe between software and a MIDI device. The software and the MIDI device must
interpret the data they exchange and act accordingly.
The MIDI Port supports the following two feature types:
• Legacy (MPU-401)
• Enhanced
Legacy. These include all features supported by MPU-401 UART mode. They can all be operated via the Legacy I/O ad-
dress space of two bytes, traditionally allocated for the MIDI Port.
Enhanced. These features extend the capabilities of the MIDI Port. They can only be operated if the MIDI is allocated with
an address space of at least three bytes.
The basic system configuration of the MIDI Port consists of the port itself, a single pull-up resistor for the MDRX pin, and a
MIDI compliant device. This system configuration is shown in Figure 38. The purpose of the pull-up resistor is to make sure
that the MIDI Port senses an inactive (high) MIDI receive signal in the absence of a MIDI device.
MIDI
Port
MIDI Receive ^{MDRX Pin}
R
MIDI Transmit
MIDI Transmit
MDTX Pin
MIDI Receive
Figure 38. MIDI System Configuration
11.2 FUNCTIONAL DESCRIPTION
The MIDI Port consists of five major functional blocks:
q _{Internal Bus Interface Unit}
q _{Port Control and Status Registers}
q _{Data Buffers and FIFOs}
q _{MIDI Communication Engine}
q _{MIDI Signals Routing Control Logic}
See Figure 39 for a block diagram of the MIDI Port.
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