
PSB 7230
Interfaces and Memory Organization
Semiconductor Group
41
Data Sheet 1998-07-01
Indirect Access to Configuration and Control Registers
Writing of hardwired registers (Configuration and Control registers) in the DSP memory
(from 2000
H
to 203F
H
) can be effected through the Parallel Host Interface.
For the last case two directly accessible locations are provided in the DSP/Host Com
area (Host addresses 40
H
and 41
H
). A write operation in the first of these registers with
a command (read/write) and a 6-bit address offset will cause the DSP to read or write a
configuration/control register in address space 2000
H
- 203F
H
. The second location
(Host address 41
H
) contains the data read/written from/to the requested location.
The procedure is described in
Table 11
.
DSP
Address
DSP Write
(Always
16 bit Wide)
Reg Data
DSP
→
Host
RDY(LSBit)
DSP Read
(always
16 bit Wide)
Reg Data
Host
→
DSP
Conf/Cont
Reg Address
Host
Address
AD0-7
41
H
Host Write
(Always
8 Bit Wide)
Reg Data
Host
→
DSP
Conf/Cont
Reg Address
Host Read
(Always
8 Bit Wide)
Reg Data
DSP
→
Host
RDY(LSBit)
3041
H
3040
H
40
H
Table 11
For reading a register
from address
(2000
H
+ a5:0)
Host writes byte: 1 0 a5 a4 a3 a2 a1 a0 to address 40
H
. This
causes RDY bit to be set to 0. Internally, an RACC interrupt
status (INT1 line) is generated to the DSP.
Firmware:
DSP reads address 3040
H
, recognizes a “read” access
(most significant bit = 1), fetches data from (2000
H
+ a5:0),
writes into 3041
H
and sets RDY bit (address 3040
H
/40
H
) to ‘1’.
After polling RDY bit to be ‘1’, the host can read the data from
41
H
, and access 40
H
for another operation.
Host writes data into address 41
H
.
Host writes byte: 0 0 a5 a4 a3 a2 a1 a0 to address 40
H
.
This causes RDY bit to be set to 0. Internally, an RACC interrupt
status (INT1 line) is generated to the DSP.
Firmware:
DSP reads address 3040
H
, recognizes a “write” access
(most significant bit = 0), fetches data from 3041
H
, writes it into
(2000
H
+ a5:0), and sets RDY bit (address 3040
H
/40
H
) to ‘1’.
After polling RDY bit to be ‘1’, the host can access 40
H
for
another operation.
For writing a register
at address
(2000
H
+ a5:0)