Motorola DSP56301 - Manual (Page 156)

HI32 DSP-Side Programming Model
6 -38 DSP56301 User’s Manual
6.7.6 DSP PCI Status Register (DPSR)
.
A 24-bit read-only status register by which the DSP56300 core examines the status and flags
of the HI32 in PCI mode (DCTR[HM]
=
$1). The host processor cannot access the DPSR.
23 22 21 20 19 18 17 16
RDC5 RDC4 RDC3 RDC2 RDC1 RDC0
15 14 13 12 11 10 9 8
RDCQ MDT HDTC TO TRTY TDIS TAB
7 6 5 4 3 2 1 0
MAB DPER APER MARQ MRRQ MTRQ MWS
Reserved. Write to 0 for future compatibility
Figure 6-10. DSP PCI Status Register (DPSR)
Table 6-15. DSP PCI Status Register (DPSR) Bit Definitions
Bit Number Bit Name Reset Value Description
23–22 0 Reserved. Write to 0 for future compatibility.
21–16 RDC[5–0] Remaining Data Count
Read-only bits that indicate the PCI data phases remaining to complete a
PCI burst after the HI32 completes a transaction as a PCI master.
RDC[5–0] are updated each time a transaction terminates and the HI32 is
a PCI master (MARQ = 1).
If the transaction terminates normally, the
value of RDC[5–0] is $00 and TO = 0, TRTY = 0, TDIS = 0, TAB = 0, MAB
= 0. If the master access counter is enabled and the burst does not
complete for any reason, the value of RDC[5–0] is the remaining number
of data phases remaining to complete the burst minus one (that is, RDC =
$2 signifies that three more words must be transferred to complete the
burst). The length of the burst is limited by BL[5–0] in the DPMC.
If the
master counter is disabled (DPCR[MACE] is cleared), the RDC[5–0] and
RDCQ bits are not valid.
Note: Typical reasons why a burst does not complete are a
target-initiated transaction termination or a requirement that the
HI32 generate a master-initiated time-out transaction
termination.
15 RDCQ Remaining Data Count Qualifier
Qualifies the value of the DPSR[RDC] bits. If the MDT bit is cleared
(MARQ = 1) at the end of a transaction initiated by the HI32 (that is, not all
the master data transferred), the burst length for the next transaction to
the same target to complete the data transfer is calculated as follows:
BL[5–0] = RDC[5–0] + RDCQ
Note: If any of the DPSR[TAB/TRTY/MAB] status bits are set, the
transaction can be initiated again with the same address and
burst length by writing the DPAR with its previous value. If the
master counter is disabled (DPCR[MACE] is cleared), the
RDC[5–0] and RDCQ bits are not valid.