Host Port Configuration - Motorola DSP56303 User Manual

Table 2-10. Host Port Usage Considerations (Continued)
Action
Asynchronous write to transmit
byte registers
Asynchronous write to host
vector
2.7.2

Host Port Configuration

HI08 signal functions vary according to the programmed configuration of the interface as
determined by the 16 bits in the HI08 Port Control Register (HPCR). Refer to the Chapter 6,
Host Interface (HI08), for detailed descriptions of HI08 configuration registers.
Signal Name Type
H[0–7] Input/Output
HAD[0–7] Input/Output
PB[0–7] Input or
Output
HA0 Input
HAS/HAS Input
PB8 Input or
Output
The host interface programmer should 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.
The host interface programmer must change the Host Vector (HV) register only when the
Host Command bit (HC) is clear. This practice guarantees that the DSP interrupt control
logic receives a stable vector.
Table 2-11. Host Interface
State During
1
Reset or Stop
Disconnected Host Data—When the HI08 is programmed to interface with a
internally non-multiplexed host bus and the HI function is selected, these signals
are lines 0–7 of the Data bus.
Host Address—When the HI08 is programmed to interface with a
multiplexed host bus and the HI function is selected, these signals are
lines 0–7 of the Address/Data bus.
Port B 0–7—When the HI08 is configured as GPIO through the HPCR,
these signals are individually programmed through the HI08 Data
Direction Register (HDDR).
This input is 5 V tolerant.
Disconnected Host Address Input 0—When the HI08 is programmed to interface
internally with a non-multiplexed host bus and the HI function is selected, this
signal is line 0 of the Host Address bus.
Host Address Strobe—When the HI08 is programmed to interface
with a multiplexed host bus and the HI function is selected, this signal is
the Host Address Strobe (HAS) Schmitt-trigger input. The polarity of the
address strobe is programmable, but is configured active-low (HAS)
following reset.
Port B 8—When the HI08 is configured as GPIO through the HPCR,
this signal is individually programmed through the HDDR.
This input is 5 V tolerant.
Signals/Connections
Description
Signal Description
Host Interface (HI08)
2-11