
PSB 7280
Semiconductor Group
83
Data Sheet 1998-07-01
4.5
Programming Indirectly Accessible Registers
Registers in the memory mapped (DSP X-data RAM) area from 2000
H
upwards are read
and written:
– via the Parallel Host Interface by using two registers (Conf/Cont Reg Address Register
at address 40
H
/3040
H
and Conf/Control Reg Data Register at address 41
H
/3041
H
)
4.5.1
For writing a configuration/control register (addresses 2000
H
-203F
H
), the host writes in
the data register the data byte to be written and in the address register the write
command:
Programming via Parallel Host Interface
(see also
Chapter 3.3.2
)
where A(5:0) gives the offset of the register to be written. This causes an RACC
(Register Access) interrupt status to the DSP. The DSP software transfers the data byte
to the requested address 2000
H
+ A(5:0) and writes the RDY bit (least significant bit of
address 40
H
/3040
H
) to ‘1’ again (which was set to ‘0’ by hardware at the time of writing
of the address register). By sensing the state of bit RDY the host is able to start a new
access to address and data registers when the DSP is ready.
For reading a configuration/control register (addresses 2000
H
- 203F
H
), the host writes
in the address register the read command:
where A(5:0) gives the offset of the register to be read. This causes a RACC (Register
Access) interrupt status to the DSP. The DSP software transfers the contents of the
requested address 2000
H
+ A(5:0) into the data register and writes the RDY bit to ‘1’.
Bit 7
Bit 0
0
0
A5
A4
A3
A2
A1
A0
Bit 7
Bit 0
1
0
A5
A4
A3
A2
A1
A0