LPC47M14X datasheet(74/205 Pages) SMSC

74 / 205 page

SMSC DS – LPC47M14X

Page 74

Rev. 03/19/2001

Registers (Ports)

The run-time registers in the MPU-401 Host Interface are shown below in Table 34.

Table 34 – MPU-401 Host Interface Registers

ADDRESS

TYPE

DESCRIPTION

MIDI DATA

MPU-401 I/O Base Address

R/W

Used for MIDI transmit data, MIDI

receive data, and MPU-401 command

acknowledge.

STATUS

MPU-401 I/O Base Address + 1

Used to indicate the send/receive status

of the MIDI Data port.

COMMAND

MPU-401 I/O Base Address + 1

Used for MPU-401 Commands.

6.8.3

MIDI Data Port

The MIDI Data port exchanges MIDI transmit and MIDI receive data between the MPU-401 UART interface and the

host. The MIDI Data port is read/write (Table 35). The MIDI Data port is also used to return the command

acknowledge byte ‘FEh’ following host writes to the COMMAND port.

The MIDI Data port is full-duplex; i.e., the transmit and receive buffers can be used simultaneously.

An interrupt is generated when either MIDI receive data or a command acknowledge is available to the host in the

MIDI Data register. See Section “Bit 7 – MIDI Receive Buffer Empty” and “Interrupt”

Table 35 – MIDI Data Port

MPU-401 I/O BASE ADDRESS

DEFAULT

TYPE

R/W

n/a

NAME

MIDI DATA/COMMAND-ACKNOWLEDGE REGISTER

6.8.4

Status Port

The Status port is used to indicate the state of the transmit and receive buffers in the MIDI Data port. The Status port

is read-only (Table 36). Status port Bit 6 is MIDI Transmit Busy, Bit 7 is MIDI Receive Buffer Empty. The remaining

bits in the Status port are RESERVED.

Table 36 – MPU-401 Status Port

MPU-401 I/O BASE ADDRESS+1

DEFAULT

TYPE

0x80

BIT

NAME

MIDI RX

BUFFE

EMPTY

MIDI TX

BUSY

Bit 7 – MIDI Receive Buffer Empty

Bit 7 MIDI Receive Buffer Empty indicates the read state of the MIDI Data port (Table 37). If the MRBE bit is ‘0’, MIDI

Read/Command Acknowledge data is available to the host.

If the MRBE bit is ‘1’, MIDI Read/Command

Acknowledge data is NOT available to the host.

The MPU-401 Interrupt output is active ‘1’ when the MIDI Receive Buffer Empty bit is ‘0’. The MPU-401 Interrupt

output is inactive ‘0’ when the MIDI Receive Buffer Empty bit is ‘1’. See Section “Interrupt” for more information.

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