
Operation
respectively. When host requests are enabled, the host request pins operate as shown in
Figure7
Status
0
$2 HREQ
0
0
HF3
HF2
TRDY
TXDE RXDF ISR
Host Request
Signals
Host Request
Asserted
7
0
HRRQ
HREQ
HTRQ
$0
INIT
0
0
HF1
HF0 HLEND TREQ RREQ ICR
Enable
Figure 6-3. HI08 Host Request Structure
Table 6-5 shows the operation of the HREQ pin when a single request line is used. The host can
test these ICR bits to determine the interrupt source.
Table 6-5. HREQ Pin Operation In Single Request Mode (ICR[2] = HDRQ = 0)
ICR[1] = TREQ
0
0
1
1
ICR[0] = RREQ
0
1
0
1
HREQ Pin
No interrupts
RXDF request enabled
TXDE request enabled
RXDF and TXDE request enabled
Table 6-6 shows the operation of the transmit request ( HTRQ ) and receive request ( HRRQ ) lines
with dual host requests enabled.
Table 6-6. HTRQ and HRRQ Pin Operation In Double Request Mode (ICR[2] = HDRQ = 1)
ICR[1] = TREQ
0
0
1
1
ICR[0] = RREQ
0
1
0
1
HTRQ Pin
No interrupts
No interrupts
TXDE Request enabled
TXDE Request enabled
HRRQ Pin
No interrupts
RXDF request enabled
No interrupts
RXDF request enabled
6.4.5 Endian Modes
The Host Little Endian bit in the host-side Interface Control Register (ICR[5] = HLEND) allows
the host to access the HI08 data registers in Big Endian or Little Endian mode. In Little Endian
mode (HLEND = 1), a host transfer occurs as shown in
Figure 6-4 .DSP56311 User’s Manual, Rev. 2
Freescale Semiconductor
6-9