AD1821 Analog Devices, AD1821 Datasheet - Page 38

• Manufacturer Part Number: AD1821
• Manufacturer: Analog Devices

AD1821
MIDI and MPU-401 Registers
The AD1821 contains a set of ISA Bus registers (ports) that correspond to those used by the ISA bus MIDI audio interface cards.
Table XI lists the ISA Bus MIDI registers. These registers support commands and data transfers described in MIDI 1.0 Detailed
Specification and Standard MIDI Files 1.0, © 1994, MIDI Manufacturers Association, PO Box 3173 La Habra, CA 90632-3173.
NOTES
The AD1821 supports only the MIDI 0xFF (reset) and 0x3F (pass-through mode) commands. The controller powers setup for intel-
ligent MIDI mode, but must be put in pass-through mode. To start MIDI operations, send a reset command (0xFF) and then send a
pass-through mode command (0x3F). The MIDI data register contains an acknowledge byte (0xFE) after each command transfer.
All commands return an ACK byte in “smart” mode.
Status commands (0xAx) return ACK and a data byte; all other commands return ACK.
All commands except reset (0xFF) are ignored in UART mode. No ACK bytes are returned.
“Smart” mode data transfers are not supported.
Game Port Registers
The AD1821 contains a Game Port ISA Bus Register that corresponds to the game port described in the PnP specification.
DSR (R)
DRR (R)
CMD [7:0] (W)
0x(MIDI Base+1)
STATE
NAME
BIT
Register Name
MIDI Data (r/w)
MIDI Status (r), Command (w)
Register Name
Music0: Address (w), Status (r)
Music0: Data (w)
Music1: Address (w)
Music1: Data (w)
Register Name
Game Port I/O
Data Send Ready. When read, this bit indicates that you can (0) or cannot (1) write to the
MIDI Data register. (Full = 1, Empty = 0)
Data Receive Ready. When read, this bit indicates that you can (0) or cannot (1) read from the
MIDI Data register. (Unreadable = 1, Readable = 0)
MIDI Command. Write MPU-401 commands to bits [7:0] of this register.
DRR
7
1
DSR
6
0
Table XII. Game Port ISA Bus Registers
Table XI. MIDI ISA Bus Registers
Table X. AdLib ISA Bus Registers
5
0
Address
0x(MIDI Base) Relocatable in range 0x008 to 0x3F8
0x(MIDI Base+1)
–38–
ISA Bus Address
0x(Adlib Base) Relocatable in range 0x008 – 0x3F8
0x(Adlib Base+1)
0x(Adlib Base+2)
0x(Adlib Base+3)
Address
0x(Game Port Base+0 to Game Port Base+7
Relocatable in the range 0x100 to 0x3F8
4
0
3
0
RESERVED
2
0
1
0
0
0
REV. 0