Motorola DSP56012 - Manual (Page 104)

4-24 DSP56012 User’s Manual MOTOROLA
Parallel Host Interface
Host Interface (HI)
4.4.5.3 Interrupt Control Register (ICR)
The Interrupt Control Register (ICR) is an 8-bit read/write control register used by
the host processor to control the HI interrupts and flags. The ICR cannot be accessed
by the DSP CPU. The ICR is a read/write register that allows the use of bit
manipulation instructions on control register bits. The control bits are described in
the following paragraphs.
4.4.5.3.1 ICR Receive Request Enable (RREQ)—Bit 0
The Receive Request Enable (RREQ) bit is used to control the HOREQ pin for host
receive data transfers. In Interrupt mode (DMA off), RREQ is used to enable
interrupt requests via the external HI Request (HOREQ) 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 HOREQ 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 HOREQ pin to request data transfer.
Note: Hardware reset, software reset, individual reset, and Stop clear RREQ.
4.4.5.3.2 ICR Transmit Request Enable (TREQ)—Bit 1
The Transmit Request enable (TREQ) bit is used to control the HOREQ pin for host
transmit data transfers. In Interrupt mode (DMA off), TREQ is used to enable
interrupt requests via the external HOREQ 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 HOREQ pin will be asserted if TXDE is set.
Figure 4-11 HI Register Map
AA0320k
$0
$1
$2
$3
$4
$5
$6
$7
Interrupt Control
Command Vector
Interrupt Status
Interrupt Vector
Unused
Receive/Transmit
Bytes
ICR
CVR
ISR
IVR
0 0 0 0 0 0 0 0
RXH/TXH
RXM/TXM
RXL/TXL
Host Address
HOA[2:0]
HI Data Bus
H[7:0]