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Host Interface (HDI08)
HDI08 – DSP-Side Programmer's Model
8.5
HDI08 – DSP-SIDE PROGRAMMER'S MODEL
The DSP core threats the HDI08 as a memory-mapped peripheral occupying eight 24-bit
words in X data memory space. The DSP may use the HDI08 as a normal memory-mapped
peripheral, employing either standard polled or interrupt-driven programming techniques.
Separate transmit and receive data registers are double-buffered to allow the DSP and host
processor to transfer data efficiently at high speed. Direct memory mapping allows the DSP
core to communicate with the HDI08 registers using standard instructions and addressing
modes. In addition, the MOVEP instruction allows direct data transfers between the DSP
memory and the HDI08 registers or vice-versa. The HOTX and HORX registers may be
serviced by the on-chip DMA controller for data transfers.
The eight host processor registers consists of two data registers and six control registers. All
registers can be accessed by the DSP core but not by the external processor.
Data registers are 24-bit registers used for high-speed data transfer to and from the DSP. They
are as follows:
•
Host Data Receive Register (HORX)
•
Host Data Transmit Register (HOTX)
The control registers are 16-bit registers used to control the HDI08 functions. The eight MSBs
in the control registers are read by the DSP as zero. The control registers are as follows:
•
Host control register (HCR)
•
Host status register (HSR)
•
Host base address register (HBAR)
•
Host port control register (HPCR)
•
Host GPIO data direction register (HDDR)
•
Host GPIO data register (HDR)
Hardware and software reset disable the HDI08. After reset, the HDI08 signals are configured
as GPIO with all pins disconnected.
8.5.1
HOST RECEIVE DATA REGISTER (HORX)
The 24-bit read-only HORX register is used for host-to-DSP data transfers. The HORX
register is loaded with 24-bit data from the transmit data registers (TXH:TXM:TXL) on the
host side when both the transmit data register empty TXDE (host side) and host receive data
8-6
DSP56367
MOTOROLA
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