Dsp Master Transmit Data Register (Dtxm) - Motorola DSP56305 User Manual

HOST INTERFACE (HI32)
DSP SIDE Programming Model
DSP56300 core writes 24-bit words to the DTXS. The data is output, a word at a time, to
the bus from the HRXS.
In PCI target data transfers (HM = $1) with HRF = $0, the slave DSP-to-host data path is
a three word deep, 32-bit wide FIFO. The DSP56300 core writes 24-bit words to the
DTXS. Each word written by the DSP56300 core contains 16-bits of significant data, right
aligned, the most significant byte is not transmitted. The first word written by the
DSP56300 core contains the two least significant bytes of the 32-bit word to be output
from the HRXS. The second word written by the DSP56300 core contains the two most
significant bytes of the 32-bit word be output from the HRXS. Each time the host reads a
32-bit word from the HRXS, the 32-bits of significant data located in two locations of the
slave DSP-to-host data path (DTXS and HRXS) are output.
The DSP side of the DSP-to-host data FIFOs are described in the following pages. For a
detailed description of the host side see Section 6.6.4 and Section 6.6.5.
6.5.10

DSP Master Transmit Data Register (DTXM)

The 24-bit wide DSP master transmit data register (DTXM) is the input stage of the
master DSP-to-host data path FIFO used for DSP-to-host master data transfers in the PCI
mode (HM = $1).
The DTXM may be written if the MTRQ bit is set in the DPSR. Data should not be
written to the DTXM until MTRQ is set to prevent previous data from being overwritten.
Filling the DTXM by DSP56300 core writes (MOVE(P) instructions or DMA transfers)
clears MTRQ. The DSP56300 core may set the MTIE bit to cause a host receive data
interrupt when MTRQ is set.
In the PCI mode (HM = $1) the DSP56300 core can clear the HI32 master-to-host bus data
path and empty DTXM by setting the CLRT bit in the DPCR.
In the 32-bit mode (HM = $1 with FC = $0), only the two least significant bytes of the
DTXM are transferred. (See Section 6.5.9, above, and Table 6-5).
Hardware, software and personal software resets empty the DTXM.
MOTOROLA DSP56305 User's Manual 6-45