RCVDL56DPFL/SP, RCV56DPFL/SP, and RCV336DPFL/SP Designer’s Guide
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4. DSP RAM ACCESS
The MDP DSP contains a 16-bit wide random access memory (RAM). The host processor can access (read or write) the
RAM through a 12-bit memory address in registers 1D and 1C.
4.1 INTERFACE MEMORY ACCESS TO DSP RAM
The interface memory acts as an intermediary during host to DSP RAM or DSP RAM to host data exchanges. The address
stored in interface memory RAM address registers MEADDH and MEADDL by the host is the DSP RAM address for data
access. The data is transferred through data registers MEDAM and MEDAL.
One or two bytes (1 byte = 8 bits) are transferred between DSP RAM and DSP interface memory once each device cycle.
The DSP operates at a 7200 Hz sample rate.
The RAM access bit (MEACC) in the interface memory instructs the DSP to access the RAM. The transfer is initiated by the
host setting the MEACC bit. The DSP tests this bit each sample period.
RAM can be accessed using one of four methods:
1. 8-bit read - 8-bit write.
2. 16-bit read - 8-bit write.
3. 16-bit read - 16-bit write.
4. 16-bit read only (MDP diagnostics).
Parameters transferred under the first method have only 8 bits of significance. The data is written to and read from MEDAL.
Data in MEDAM is ignored.
Parameters transferred using the second method have 16 bits of significance but can be written only 8 bits at a time. These
parameters have two access codes associated with them, one for the least significant 8-bits and one for the most significant
8 bits. The host need read only the low address to obtain both the most significant and the least significant bytes of the data
if the two access codes are in consecutive order.
Parameters transferred using the third method involve 16-bit read or write operations using one access code.
Finally, all diagnostic read operations using the fourth method use only one access code. Data is read from MEDAM and
MEDAL.
The parameters available in DSP RAM are listed in Table 4-1.
Summary of Contents for RC336DPFL
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