Expansion Bus Host Port Operation
8-23
Expansion Bus
8.5.1
Expansion Bus Host Port Registers Description
8.5.1.1
Expansion Bus Data Register
The expansion bus data (XBD) register, shown in Figure 8–14, contains the
data that was read from the memory accessed by the expansion bus host port
if the current access is a read, or the data that is written to the memory if the
current access is a write.
This register is used when expansion host port operates either in synchronous
or asynchronous mode.
Figure 8–14. Expansion Bus Data Register
31
0
XBD
HRW,+0000 0000 0000 0000 0000 0000 0000 0000
8.5.1.2
Expansion Bus Internal Slave Address Register
The expansion bus internal slave address (XBISA) register is used when the
external expansion bus master initiates data transfer. This register controls the
memory location in the DSP memory map being accessed by the external
mastering data transactions. This address is a 30-bit word address. The two
LSB bits in this register are used by the host to enable or disable autoincrement
of XBISA register, and to trigger the interrupt (by setting the DSPINT bit).The
XBISA register is shown in Figure 8–15 and described in Table 8–14.
Figure 8–15. Expansion Bus Internal Slave Address Register (XBISA)
31
2
1
0
XBSA
AINC
DSPINT
HRW,+0000 0000 0000 0000 0000 0000 0000 00
HRW, +0
HRW, +0
Table 8–14. XBISA Register Description
Field
Description
DSPINT
The external master to DSP interrupt. Used to wake up the DSP
from reset. This bit is cleared by corresponding bit in the XBHC.
AINC
Enable autoincrement. (Asynchronous mode only)
AINC = 0:
XBD register is accessed with autoincrement of XBSA
field.
AINC = 1:
XBD register is accessed without autoincrement of
XBSA field.
XBSA
30-bit word address. The XBSA bit-field controls memory location
in the DSP memory map being accessed by the host.