HOST INTERFACE (HI)
5 - 34
PORT B
MOTOROLA
as a general purpose I/O pin called PB14. When the port is defined as the host interface,
the user may manipulate the Port B Control register to program this input as either PB14,
or as the HACK pin. The table below shows the Port B Control register bit configurations.
HACK may act as a data strobe for HI DMA data transfers (See Figure 5-18). Or, if HACK
is used as an MC68000 host interrupt acknowledge, it enables the HI interrupt vector reg-
ister (IVR) on the host data bus H0-H7 if HREQ is asserted (See Figure 5-16). In this case,
all other HI control pins are ignored and the state of the HI is not affected.
Note: HACK should always be pulled high when it is not in use.
5.3.5
Servicing the Host Interface
The HI can be serviced by using one of the following protocols:
1. Polling
2. Interrupts, which can be either
a. non-DMA
b. DMA
From the host processor viewpoint, the service consists of making a data transfer since
this is the only way to reset the appropriate status bits.
HA0 - HA2
HR/W
HEN
H0 - H7
DSP56002
HA0 - HA2
HR/W
HEN
H0 - H7
HREQ
HACK
WRITE
READ
DATA
LATCHED
IN HI
8
3
+5 V
+5 V
Figure 5-15 Host Processor Transfer Timing
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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