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ADSP-2186L Datasheet(PDF) 9 Page - Analog Devices |
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ADSP-2186L Datasheet(HTML) 9 Page - Analog Devices |
9 / 34 page ADSP-2186L –9– REV. A Boot Memory Select ( BMS) Disable The ADSP-2186L also lets you boot the processor from one external memory space while using a different external memory space for BDMA transfers during normal operation. You can use the CMS to select the first external memory space for BDMA transfers and BMS to select the second external memory space for booting. The BMS signal can be disabled by setting Bit 3 of the System Control Register to 1. The System Control Register is illustrated in Figure 7. 0 0 0 0 0 1 00 00 0 0 0 1 1 1 15 14 13 12 11 10 9 8 7 6 5 4321 0 DM (0 3FFF) SYSTEM CONTROL REGISTER SPORT0 ENABLE 1 = ENABLED, 0 = DISABLED SPORT1 ENABLE 1 = ENABLED, 0 = DISABLED SPORT1 CONFIGURE 1 = SERIAL PORT 0 = FI, FO, IRQ0, IRQ1, SCLK PWAIT PROGRAM MEMORY WAIT STATES BMS ENABLE 0 = ENABLED, 1 = DISABLED Figure 7. System Control Register Byte Memory The byte memory space is a bidirectional, 8-bit-wide, external memory space used to store programs and data. Byte memory is accessed using the BDMA feature. The BDMA Control Register is shown in Figure 8. The byte memory space consists of 256 pages, each of which is 16K × 8. BDMA CONTROL BMPAGE BTYPE BDIR 0 = LOAD FROM BM 1 = STORE TO BM BCR 0 = RUN DURING BDMA 1 = HALT DURING BDMA 00 0 0 0 0 00 000 0 1 0 0 0 15 14 13 12 11 10 9 8 7 6 5 43210 DM (0 3FE3) Figure 8. BDMA Control Register The byte memory space on the ADSP-2186L supports read and write operations as well as four different data formats. The byte memory uses data bits 15:8 for data. The byte memory uses data bits 23:16 and address bits 13:0 to create a 22-bit address. This allows up to a 4 meg × 8 (32 megabit) ROM or RAM to be used without glue logic. All byte memory accesses are timed by the BMWAIT register. Byte Memory DMA (BDMA, Full Memory Mode) The byte memory DMA controller allows loading and storing of program instructions and data using the byte memory space. The BDMA circuit is able to access the byte memory space while the processor is operating normally and steals only one DSP cycle per 8-, 16- or 24-bit word transferred. The BDMA circuit supports four different data formats, that are selected by the BTYPE register field. The appropriate number of 8-bit accesses is determined from the byte memory space to build the word size selected. Table V shows the data formats sup- ported by the BDMA circuit. Table V. BDMA Data Formats Internal BTYPE Memory Space Word Size Alignment 00 Program Memory 24 Full Word 01 Data Memory 16 Full Word 10 Data Memory 8 MSBs 11 Data Memory 8 LSBs Unused bits in the 8-bit data memory formats are filled with 0s. The BIAD register field is used to specify the starting address for the on-chip memory involved with the transfer. The 14-bit BEAD register specifies the starting address for the external byte memory space. The 8-bit BMPAGE register specifies the starting page for the external byte memory space. The BDIR register field selects the direction of the transfer. Finally the 14-bit BWCOUNT register specifies the number of DSP words to transfer and initiates the BDMA circuit transfers. BDMA accesses can cross page boundaries during sequential addressing. A BDMA interrupt is generated on the completion of the number of transfers specified by the BWCOUNT register. The BWCOUNT register is updated after each transfer so it can be used to check the status of the transfers. When it reaches zero, the transfers have finished and a BDMA interrupt is gener- ated. The BMPAGE and BEAD registers must not be accessed by the DSP during BDMA operations. The source or destination of a BDMA transfer will always be on-chip program or data memory, regardless of the values of Mode B, PMOVLAY or DMOVLAY. When the BWCOUNT register is written with a nonzero value, the BDMA circuit starts executing byte memory accesses with wait states set by BMWAIT. These accesses continue until the count reaches zero. When enough accesses have occurred to create a destination word, it is transferred to or from on-chip memory. The transfer takes one DSP cycle. DSP accesses to external memory have priority over BDMA byte memory accesses. The BDMA Context Reset bit (BCR) controls whether the processor is held off while the BDMA accesses are occurring. Setting the BCR bit to 0 allows the processor to continue opera- tions. Setting the BCR bit to 1 causes the processor to stop execution while the BDMA accesses are occurring, to clear the context of the processor and start execution at address 0 when the BDMA accesses have completed. Internal Memory DMA Port (IDMA Port; Host Memory Mode) The IDMA Port provides an efficient means of communication between a host system and the ADSP-2186L. The port is used to access the on-chip program memory and data memory of the DSP with only one DSP cycle per word overhead. The IDMA port cannot, however, be used to write directly to the DSP’s memory-mapped control registers. The IDMA port has a 16-bit multiplexed address and data bus and supports 24-bit program memory. The IDMA port is com- pletely asynchronous and can be written to while the ADSP- 2186L is operating at full speed. |
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