Host Port Configuration; Table 2-10 Host Port Usage Considerations - Motorola DSP56309 User Manual

Action
Asynchronous read of
receive byte registers
Asynchronous write to
transmit byte registers
Asynchronous write to
host vector
2.8.2

Host Port Configuration

The functions of the signals associated with the HI08 vary according to the programmed
configuration of the interface as determined by the HI08 Port Control Register (HPCR).
Refer to Section 6ÑHost Interface (HI08) for detailed descriptions of this and the other
configuration registers used with the HI08.
Host interface signal descriptions for the DSP56309 are listed in Table 2-11.
MOTOROLA

Table 2-10 Host Port Usage Considerations

When reading the receive byte registers, receive register high
(RXH), receive register middle (RXM), or receive register low
(RXL), use interrupts or poll the receive register data full
(RXDF) flag which indicates that data is available. This assures
that the data in the receive byte registers is valid.
Do not write to the transmit byte registers, transmit register
high (TXH), transmit register middle (TXM), or transmit
register low (TXL), unless the transmit register data empty
(TXDE) bit is set indicating that the transmit byte registers are
empty. This guarantees that the transmit byte registers transfer
valid data to the host receive (HRX) register.
Change the host vector (HV) register only when the host
command bit (HC) is clear. This guarantees that the DSP
interrupt control logic receives a stable vector.
DSP56309UM/D
Signal/Connection Descriptions
Host Interface (HI08)
Description
2-17