Interface Control Register (Icr) Bit Definitions - Motorola DSP56303 User Manual

Table 6-15. Interface Control Register (ICR) Bit Definitions
Bit Number Bit Name
7 INIT
6
5 HLEND
4 HF1
3 HF0
2 HDRQ
Reset Value
0 Initialize
The host processor uses the INIT bit to force initialization of the HI08
hardware. During initialization, the HI08 transmit and receive control bits
are configured. Whether it is necessary to use the INIT bit to initialize the
HI08 hardware depends on the software design of the interface.
The type of initialization when the INIT bit is set depends on the state of
TREQ and RREQ in the HI08. The INIT command, which is local to the
HI08, configures the HI08 into the desired data transfer mode. When the
host sets the INIT bit, the HI08 hardware executes the INIT command.
The interface hardware clears the INIT bit after the command executes.
TREQ
0
0
1
1
0 Reserved. Write to 0 for future compatibility.
0 Host Little Endian
If the HLEND bit is cleared, the host can access the HI08 in Big-Endian
byte order. If set, the host can access the HI08 in Little-Endian byte order.
If the HLEND bit is cleared the RXH/TXH register is located at address $5,
the RXM/TXM register at $6, and the RXL/TXL register at $7. If the
HLEND bit is set, the RXH/TXH register is located at address $7, the
RXM/TXM register at $6, and the RXL/TXL register at $5.
0 Host Flag 1
A general-purpose flag for host-to-DSP communication. The host
processor can set or clear HF1, and the DSP56303 can not change it.
HF1 is reflected in the HSR on the DSP side of the HI08.
0 Host Flag 0
A general-purpose flag for host-to-DSP communication. The host
processor can set or clear HF0, and the DSP56303 cannot change it. HF0
is reflected in the HSR on the DSP side of the HI08.
0 Double Host Request
If cleared, the HDRQ bit configures HREQ/HTRQ and HACK/HRRQ as
HREQ and HACK, respectively. If HDRQ is set, HREQ/HTRQ is
configured as HTRQ, and HACK/HRRQ is configured as HRRQ.
Host Interface (HI08)
Description
After INIT
RREQ
Execution
0 INIT = 0
1 INIT = 0;
RXDF = 0; HTDE = 1
0 INIT = 0;
TXDE = 1; HRDF = 0
1 INIT = 0;
RXDF = 0; HTDE =
1; TXDE = 1;
HRDF = 0
Host Programmer Model
Transfer Direction
Initialized
None
DSP to host
Host to DSP
Host to/from DSP
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