
7.7.2 HOST INTERFACE 
SMSC DS – LPC47M192 
Page 79 
Rev. 03/30/05 
DATASHEET 
Overview 
The Host Interface includes two contiguous 8-bit run-time registers (the Status/Command Port and the Data Port), 
and an interrupt.  For illustration purposes, the Host Interface block shown in FIGURE 2 uses standard ISA signaling.  
Address decoding and interrupt selection for the Host Interface are determined by device configuration registers (see 
Section “MPU-401Configuration Registers”). 
I/O Addresses 
The Sound Blaster 16 MPU-401 UART mode MIDI interface requires two consecutive I/O addresses with possible 
base I/O addresses of 300h and 330h.  The default is 330h.  The LPC47M192 MPU-401 I/O base address is 
programmable on even-byte boundaries throughout the entire I/O address range (see Section “Activate and I/O Base 
address”). 
Registers (Ports) 
The run-time registers in the MPU-401 Host Interface are shown below in Table 33. 
Table 33  –  MPU-401 HOST INTERFACE REGISTERS 
REGISTER NAME 
MIDI DATA 
ADDRESS 
TYPE 
R/W 
DESCRIPTION 
MPU-401 I/O Base Address 
Used for MIDI transmit data, MIDI 
receive data, and MPU-401 command 
acknowledge. 
Used to indicate the send/receive status 
of the MIDI Data port. 
Used for MPU-401 Commands.  
STATUS  
MPU-401 I/O Base Address + 1 
R 
COMMAND 
MPU-401 I/O Base Address + 1 
W 
7.7.3 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 34). 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 34  - MIDI Data Port 
MPU-401 I/O BASE ADDRESS
D5
D4
R/W
R/W
D7
R/W
MIDI DATA/COMMAND-ACKNOWLEDGE REGISTER 
D6
R/W
D3
R/W
D2
R/W
D1
R/W
D0
R/W
DEFAULT
n/a 
TYPE
NAME
7.7.4 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 35).  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 35  - MPU-401 STATUS PORT 
TYPE 
BIT 
NAME 
MPU-401 I/O BASE ADDRESS+1
D7
D6
R 
R 
MIDI RX 
BUFFER 
EMPTY 
DEFAULT
0x80 
D5
R 
0 
D4
R 
0 
D3
R 
0 
D2
R 
0 
D1
R 
0 
D0
R 
0 
MIDI TX 
BUSY 
7.7.4.1 
Bit 7 MIDI Receive Buffer Empty indicates the read state of the MIDI Data port (Table 36).  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. 
Bit 7 – MIDI Receive Buffer Empty