Sundance SMT300Q v.1.6 - Manual (Page 33)

User Manual (QCF42); Version 3.0, 8/11/00; © Sundance Multiprocessor Technology Ltd. 1999
13 Global/Local Bus Transfers, DSP <-> CompactPCI.
The traditional global bus interface on C6x DSP modules interfaces to the SMT300Q
via a local bus. This allows Global bus transfers on the DSP to be converted into
local bus accesses. This allows direct DSP accesses to the CompactPCI Bridge chip.
The resources in the CompactPCI Bridge chip are illustrated in the figure below.
PCI Bridge Device
MailBox
Read/Write
Interrupt Control
Local To PCI Bus
Apperture Control
LOCAL <-> PCI
Apperture 0
16MB Address
Space
DSP Global
Bus Access
Arbitration
Unit
Local Bus
Figure 7 : Local Bus to DSP Connectivity
13.1 Mailbox Accesses
The mailbox registers can be used if small amounts of data or commands between
the CompactPCI bus and the DSP, via the local bus, need to be transferred. Rather
than sending ComPort data, and therefore require the DSP to be checking its
ComPort for commands, a mailbox write by the CompactPCI bus can be initialized to
generate an interrupt on an DSP IIOF line indicating, to the DSP, that data is
available. The CompactPCI Bridge device provides 16 8-bit mailbox registers, which
may be used to transmit and receive data between the DSP and Host.
The mailbox registers are accessed from the DSP through the Local-to-Internal
Register (LB_IO_BASE) aperture. As illustrated in section 5, table 4 of this document
this region is accessed by the DSP via a global bus access to the CompactPCI
Bridge Registers (Address : 0x1C00 0000).