Motorola DSP56305 User Manual page 211

6.6.1.7 Host Receive Data Transfer Format (HRF1-HRF0) Bits 12 and 11
The HRF1-HRF0 bits define data transfer formats for DSP-to-host communication. The
data transfer format converter (HDTFC) operates according to the specified HRF1-HRF0
(See Table 6-16).
DSP to PCI host data transfer formats (HM = $1):
• If HRF = $0 (32-bit data mode):
The two least significant bytes of two words written to the DTXS are transferred
to the HRXS. The two least significant bytes of the first word written to the DTXS
are transferred to the two least significant bytes of the HRXS. The two least
significant bytes of the second word written to the DTXS are transferred to the
two most significant bytes of the HRXS. All four HRXS bytes are output to the
HAD31-HAD0 signals.
• If HRF = $1:
The data written to the DTXS is transferred to the three least significant HRXS
bytes and output to the HAD31-HAD0 signals as right aligned and zero extended
in the most significant byte.
• If HRF = $2:
The data written to the DTXS is transferred to the three least significant HRXS
bytes and output to the HAD31-HAD0 signals as left aligned and zero filled in the
least significant byte.
• If HRF = $3:
The data written to the DTXS is transferred to the three least significant HRXS
bytes and output to the HAD31-HAD0 signals as right aligned and sign extended
in the most significant byte.
Universal Bus mode DSP to host data transfer formats (HM = $2 or $3):
• If HRF = $0:
The data written to the DTXS is transferred to the HRXS and output to the HI32
data signals HD23-HD0.
• If HRF = $1 or $2:
The two least significant bytes of the data written to the DTXS is transferred to the
HRXS and output to the HI32 data signals HD15-HD0.
• If HRF = $3:
The two most significant bytes of the data written to the DTXS is transferred to
the HRXS and output to the HI32 data signals HD15-HD0.
MOTOROLA DSP56305 User's Manual
HOST INTERFACE (HI32)
HOST SIDE Programming Model
6-63