HOST INTERFACE (HI)
5 - 22
PORT B
MOTOROLA
control bits are described in the following paragraphs.
5.3.3.2.1
ICR Receive Request Enable (RREQ) Bit 0
The RREQ bit is used to control the HREQ pin for host receive data transfers.
In interrupt mode (DMA off), RREQ is used to enable interrupt requests via the external
host request (HREQ) pin when the receive data register full (RXDF) status bit in the ISR
is set. When RREQ is cleared, RXDF interrupts are disabled. When RREQ is set, the
external HREQ pin will be asserted if RXDF is set.
In DMA modes, RREQ must be set or cleared by software to select the direction of DMA
transfers. Setting RREQ sets the direction of DMA transfer to be DSP to host and enables
the HREQ pin to request data transfer. Hardware, software, individual, and STOP resets
clear RREQ.
5.3.3.2.2
ICR Transmit Request Enable (TREQ) Bit 1
The TREQ bit is used to control the HREQ pin for host transmit data transfers.
In interrupt mode (DMA off), TREQ is used to enable interrupt requests via the external
HREQ pin when the transmit data register empty (TXDE) status bit in the ISR is set. When
TREQ is cleared, TXDE interrupts are disabled. When TREQ is set, the external HREQ
pin will be asserted if TXDE is set.
In DMA modes, TREQ must be set or cleared by software to select the direction of DMA
transfers. Setting TREQ sets the direction of DMA transfer to be host to DSP and enables
the HREQ pin to request data transfer. Hardware, software, individual, and STOP resets
clear TREQ.
ICR
CVR
ISR
IVR
0 0 0 0 0 0 0 0
RXH/TXH
RXM/TXM
RXL/TXL
INTERRUPT CONTROL
COMMAND VECTOR
INTERRUPT STATUS
INTERRUPT VECTOR
UNUSED
RECEIVE/TRANSMIT
BYTES
HOST DATA BUS
H0 - H7
$0
$1
$2
$3
$4
$5
$6
$7
HOST ADDRESS
HA0 - HA2
Figure 5-13 HI Register Map
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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Содержание DSP56002
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