DSP Side Registers
MOTOROLA
Host Interface Eight (HI8)
16-13
Preliminary
16
Host mode bits HM0 and HM1. The transmit or receive channel not in use can be used by
the Host for polled or interrupt operation by the DSP. HDMA is cleared by a DSP reset.
Note:
This bit is always 0 if HRMS = 1 since the HREQ and HACK function is
disabled and Host DMA operations are disabled.
16.8.2.3 Host Flags 0 and 1 (HF0–HF1)—Bits 4–3
The Host Flag 0-1 (HF0 and HF1) bits are used as a general purpose flags for Host-to-DSP
communication. The HF0 and HF1 bits can be set or cleared by the Host. These bits reflect
the status of Host Flags HF0 and HF1 in the Interface Control Register (ICR) on the Host
Side.
These two flags are not designated for any specific purpose, but are considered general
purpose flags. They can be used individually or as encoded pairs in a simple Host-to-DSP
communication protocol, implemented in both the DSP and the Host Processor software.
The HF0 and HF1 bits are cleared on hardware reset.
16.8.2.4 Host Command Pending (HCP)—Bit 2
The Host Command Pending (HCP) flag bit reflects the status of the HC bit in the
Command Vector Register (CVR), indicating a Host Command Interrupt is pending. The
HCP bit is set when the HC bit is set, and both bits are cleared by the HI8 hardware when
the interrupt request is serviced by the DSP core. The Host can also clear the HC bit,
thereby clearing the HCP bit as well. The HCP bit is cleared on hardware reset.
16.8.2.5 Host Transmit Data Empty (HTDE)—Bit 1
The Host Transmit Data Empty (HTDE) flag bit indicates the Host Transmit Data (HTX)
register is empty and can be written by the DSP core. The HTDE bit is set when the HTX
register is transferred to the RXH/RXL registers, and cleared when Host Transfer Date
(HTX) is written by the DSP core. When the HTDE bit is set, the HI8 generates a
Transmit Data Full DMA request. HTDE can also be set by the Host Processor using the
initialize function. The HTDE bit is set on hardware reset.
16.8.2.6 Host Receive Data Full (HRDF)—Bit 0
The Host Receive Data Full (HRDF) flag bit indicates the Host Receive Data (HRX)
register contains data from the Host Processor. The HRDF bit is set when data is
transferred from the TXH/TXL registers to the Host Receive Data (HRX) register. The
HRDF bit is cleared when the HRX register is read by the DSP core. When the HRDF bit
is set, the HI8 generates a receive data full DMA request. The HRDF bit can also be