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(R)
ST10 with MAC
Direct Memory Access using MAC
APPLICATION NOTE
Direct Memory Access uses the ST10 MAC for address generation in external memory-external memory transfers. This application note supplies the machine code for external memory - ST10 internal memory transfers, and for external memory-external memory transfers made by Direct Memory Access using the MAC. For reference, the ST10 long addressing mode is summarized. The ST10 instruction set contains special MAC instructions and two new addressing modes which supply the MAC with up to 2 new operands per instruction. The MAC contains a 16x16 multiplier, 40 bit accumulator a repeat unit and an address generator.
memory 1
Dual port RAM (Internal)
External Bus
ST10 with MAC
memory 2
Internal Memory (Flash or DRAM)
Figure 1 System overview
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Memory transfer to ST10 internal memory
It is not possible to execute code residing in the ST10 internal memory, while writing into it. The code below, must resides in another memory, e.g. external memory, X-memory, DPRAM.
mov mov mov mov mov DPPX, DPPx, R0, R1, R3, #addr_source #addr_dest #addr_beg_source #addr_beg_dest #addr_end_source ; 10 bit prefix to point source memory ; 10 bit prefix to point destination memory ; 14 LSW of the address where to copy ; 14 LSW of the address destination ; 14 LSW of the last address to transfer ; Note that it can be done with a block size ; instead of a given address. mov mov cmp R2, [R1+], R0, [R0+] R2 R3 ; Perform the copy from (R0) to R2 ; Then increment the R0 register by 2. ; Perform the copy from R2 to (R1). ; Then increment the R1register by 2. ; Compare current address (R0) to end address ; (R3). Loop until R0 >R3. ; Note that this test can be done for a given ; count. jmpr RET cc_ULE, LOOP ; Return, or RETI if done under interrupt
This machine code writes from external memory to internal memory, using the internal bus (stand-alone or super integrated).
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Memory transfer to external memory
mov mov DPPX, DPPx, #XXXX #XXXX ; 10 bit prefix to point source memory ; 10 bit prefix to point destination memory ; Solution if a 8 bit wide bus is used ; (3 lines below) EXTR mov mov mov mov #2 QX0, QR0, IDX0, R0, MRW, #1 #1 #dest ; Two following instructions used ESFR space ; Store 1 in QX0 to allow byte transfers ; Store 1 in QR0 to allow byte transfers ; 14 LSW of the address where to copy mov
This machine code writes from one external memory to another external memory, using Direct Memory Access with MAC address generation..
#source ;14 LSW of the address source #repeat ; use the maximum repeat depending on the ; timings allowed to perform copies ; Solution if a 16 bit wide bus is used
repeat MRW times CoMOV
[IDX0+], [R0+]
; Perform the copy from (R0) to (IDX0) ; Then increment the two registers by 2.
RET
; Return or RETI if done under interrupt
DMA timing analysis
For a 50 MHz ST10 using a 16-bit wide demux bus:
* Register set-up takes 400 ns and only has to be done once. * The first memory access takes 80ns. Each subsequent memory access takes 40 ns.
Note This program only takes into account the program execution time and the time taken for memory accesses (including any waitstates on the source and the destination memory).
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Long addressing mode summary
The long addressing mode uses one of the four DPP registers to specify a physical 18-bit or 24-bit address. Long 16-bit addresses are treated in two parts. Bits 0...13 specify the 14-bit data page offset, and bits 15...14 specify the Data Page Pointer (1 of 4). The lower ten bits of the selected DPP register are concatenated with the 14-bit data page offset to generate the physical 24-bit address (see figure below).
16-bit Long Address 15 selects Data Page Pointer 9 DPP0 DPP1 DPP2 DPP3 23 14 13 0
0
14-bit page offset
14 13
0
24-bit Physical Address
Figure 2 Interpretation of a 16-bit long address The following address values are used: 00= DPP0, 01 = DPP1, 10 = DPP2, 11 = DPP3. Using the value 0x8C00 for addr_beg_source, the two MSB are 10. Therefore, DDP2 is used. If DPP2 = 0x0030, the resulting physical address is 0xC0C00.
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Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a trademark of STMicroelectronics (c) 1998 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A.
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