IT8705AF Datasheet, PDF (168/185 Pages) List of Unclassifed Manufacturers – Simple Low Pin Count Input/Output (simple LPC I/O)

IT8705F
9.12.2 Operation
In the IT8705F, only two MPU-401 device instructions are available: RESET (code: FFh) and UART mode
command (code: 3Fh). After power-up reset, the interface is in the Intelligent mode (non-UART mode). In
this mode, the operation is defined below:
1. All reads of the Data port, MIDI Base+0, return the acknowledged code(FEh). Because only two
commands are available, the receive buffer is always loaded with an acknowledge code in the Intelligent
mode.
2. All writes to the Data port, MIDI Base+0, are ignored.
3. All writes to the Command port, MIDI Base+1, are monitored and acknowledged as follows:
3Fh: Set the interface into the UART mode and loads an acknowledged code (FEh) into the receive buffer
which generates an interrupt
FFh: Set the interface into the initialization condition
Others: Not implemented
UART Mode:
1. All reads of the Data port, MIDI Base+0, return the next byte in the receive buffer FIFO. The serial data
received from the MIDI_IN pin is stored in the receive buffer FIFO. The bit 7 RXS of the Status register is
updated to reflect the new receive buffer FIFO status. The receive data available interrupt will be issued
only if the FIFO has reached its programmed trigger level. The interrupts will be cleared as soon as the
FIFO drops below its trigger level. The trigger level is programmable by changing bits 2-1 of the MIDI
port Special Configuration Register, LDN8_F0h.
2.
3. All writes to the Data port, MIDI Base+0, are placed in the transmit buffer FIFO. Whenever the transmit
buffer FIFO is not empty, the data bytes are read from the buffer in turn and sent out from the MIDI_OUT
pin. The bit 6 TXS of the Status Register is updated to reflect the new transmit buffer FIFO status.
4.
5.
6. All writes to the Command port, MIDI Base+1, are monitored and acknowledged below:
FFh: Set the interface into the initialization condition. The interface returns to the intelligent mode
Others: No operation
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IT8705F V0.4