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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.

Figure 38. MIDI System Conﬁguration

11.2 FUNCTIONAL DESCRIPTION

The MIDI Port consists of five major functional blocks:

Internal Bus Interface Unit

Port Control and Status Registers

Data Buffers and FIFOs

MIDI Communication Engine

MIDI Signals Routing Control Logic

See Figure 39 for a block diagram of the MIDI Port.

MIDI

Port

MIDI Transmit

MIDI Receive

Game

Device

MIDI

Device

MIDI Receive

MIDI Transmit

MDRX Pin

MDTX Pin

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