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