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PEB 20321
PEF 20321
Local Bus Interface (LBI)
Data Sheet
166
2001-02-14
(e.g., XFIFO, CMDR), but located at different addresses. Hence it is necessary that the
state machine uses an indirect pointer mechanism to address the required registers of
the peripheral on the LBI.
Refer to LBI register description
LBI Registers
for an overview of the DMSM register
set.
DMSM Register Initialization
The user (PCI host CPU) initializes the DMSM registers with
addresses
of specific
registers (e.g., XFIFOA address is 00
H
), and control bit
positions
of the peripheral that is
attached as part of the configuration instructions.
After initialization, no further software interaction with these registers is required.
The control of the DMSM is handled by the LBI Configuration Register:
LCONF.LBIRES resets and keeps the DMSM in an initial state (same as hardware
reset state). For normal DMSM operation bit LCONF.LBIRES must be set to
‘
1
’
again.
LCONF.DCA: Ignore processing of channel A interrupts and pass everything to the
interrupt queue.
LCONF.DCB: Ignore processing of channel B interrupts and pass everything to the
interrupt queue.
DMSM Suspend Mode
PCI Direct Accesses to the peripheral registers are possible at any time (refer to
Figure 56
). If such an access is requested while the DMSM assisted data transfers are
taking place, the DMSM will go into
‘
suspend
’
mode after completing its current bus cycle
and give up the bus to the Direct Access path. The PCI Direct Access cycle (read/write)
may be extended, e.g. by using the TRDY signal.
If the PCI Direct Access is requested while the LBI does not have
‘
ownership
’
of the local
bus (i.e., it is in slave mode), then the LBI will extend the PCI cycle until it is able to get
the bus back and complete the PCI access cycle. The status of the LBI (master/slave
mode) is indicated by an interrupt (via line LINTI1 or LINTI1 & LINTI2) and the bit field
LCONF.ABM in LBI Configuration register.