NOTE: This figure is for illustration purposes only and is not intended to suggest specific implementation details.
Host Interface
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 LPC47M10x 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
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
MPU-401 I/O Base Address + 1
R
Used to indicate the send/receive
status of the MIDI Data port.
Used for MPU-401 Commands.
COMMAND
W
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
D7
D6
D5
D4
D3
D2
D1
D0
DEFAULT
TYPE
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
n/a
NAME
MIDI DATA/COMMAND-ACKNOWLEDGE REGISTER
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
MPU-401 I/O BASE ADDRESS+1
D7
R
D6
R
D5
R
0
D4
R
0
D3
R
0
D2
R
0
D1
R
0
D0
R
0
DEFAULT
0x80
TYPE
BIT
MIDI RX MIDI TX
NAME
BUFFE
R
BUSY
EMPTY
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