LPC47M192 datasheet(82/228 Pages) SMSC

82 / 228 page

SMSC DS – LPC47M192

Page 82

Rev. 03/30/05

DATASHEET

UART MODE Command

The UART MODE command is 3Fh. The UART MODE command clears the 16C550A transmit and receive FIFOs,

places the command acknowledge byte (FEh) in the MIDI Data port receive buffer, and enables the 16C550A UART

for transmit and receive operations.

In UART mode, the MPU-401 Interface passes MIDI read and write data directly between the host (using the MIDI

Data port) and the 16C550A UART Transmit and Receive buffers.

The MPU-401 Command Controller ignores the UART MODE command when the MPU-401 Interface is already in

UART mode.

The MPU-401 RESET command is executed but not acknowledged by the MPU-401 Command Controller in UART

MODE (see Section “RESET Command”, above).

Command Acknowledge Byte

Under certain conditions, the command controller acknowledges the RESET and UART MODE commands with a

command acknowledge byte (FEh).

The command acknowledge byte appears as read-data in the MIDI Data port.

Note:

The command acknowledge byte will appear as the next available data byte in the receive buffer of the MIDI

Data port. For example if the receive FIFO is not empty when an MPU-401 RESET command is received, the

command acknowledge will appear first, before any unread FIFO data. In the examples above, the receive FIFO is

cleared before the command acknowledge byte is placed in the MIDI Data port read buffer.

7.7.6 MIDI UART

Overview

The UART is used to transmit and receive MIDI protocol data from the MIDI Data port in the Host Interface (see

Section “Host Interface”).

The MIDI protocol requires 31.25k Baud (

±1%) and 10 bits total per frame: 1 start bit, 8 data bits, no parity, and 1

stop bit. For example, there are 320 microseconds per serial MIDI data byte. MIDI data is transferred LSB first

(Figure 7).

The UART is configured in full-duplex mode for the MPU-401 MIDI Interface, with 16-byte send/receive FIFOs.

MIDI RX CLOCK

MIDI RX DATA BYTE (01H)

MIDI_IN

FIGURE 4 - MIDI DATA BYTE EXAMPLE

Note

MIDI RX CLOCK is the MIDI bit clock. The MIDI bit clock period is 32

µs.

7.7.7 MPU-401 CONFIGURATION REGISTERS

The LPC47M192 configuration registers are in Logical Device B (see “Configuration” section). The configuration

registers contain the MPU-401 Activate, Base Address and Interrupt select. The defaults for the Base Address and

Interrupt Select configuration registers match the MPU-401 factory defaults.

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