NXP Semiconductors LPC43 Series User Manual

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NXP Semiconductors LPC43 Series User Manual Manual pdf 1166 page image

UM10503 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.User manual Rev. 1.3 — 6 July 2012 1166 of 1269NXP Semiconductors UM10503Chapter 45: LPC43xx DAC45.5.3 D/A Converter Counter Value registerThis read/write register contains the reload value for the Interrupt/DMA counter.45.6 Functional description45.6.1 DMA counterWhen the counter enable bit CNT_ENA in DAC CTRL register is set, a 16-bit counter willbegin counting down, at the rate selected by CLK_APB3_DAC, from the valueprogrammed into the DAC CNTVAL register. The counter is decremented each time thecounter reaches zero, the counter will be reloaded by the value of the DAC CNTVALregister and the DMA request bit INT_DMA_REQ will be set in hardware.Note that the contents of the DAC CTRL and DAC CNTVAL registers are read and writeaccessible, but the timer itself is not accessible for either read or write.Table 1019.D/A Control register (CTRL - address 0x400E 1004) bit descriptionBit Symbol Value Description Resetvalue0 INT_DMA_REQ DMA request 00 This bit is cleared on any write to the DAC CR register.1 This bit is set by hardware when the timer times out.1 DBLBUF_ENA DMA double-buffering 00 Disable double-buffering.1 Enable double-buffering. When this bit and theCNT_ENA bit are both set, the double-buffering featurein the DAC CR register will be enabled. Writes to theDAC CR register are written to a pre-buffer and thentransferred to the DAC CR on the next time-out of thecounter.2 CNT_ENA DMA time-out 00 Time-out counter operation is disabled.1 Time-out counter operation is enabled.3 DMA_ENA DAC and DMA enable 00 Disable DMA/DMA.1 Enable DAC and DMA Burst Request Input 15 (seeTable 270).31:4 - Reserved, user software should not write ones toreserved bits. The value read from a reserved bit is notdefined.-Table 1020:D/A Converter counter value register (CNTVAL - address 0x400E 1008) bitdescriptionBit Symbol Description Reset value15:0 VALUE 16-bit reload value for the DAC interrupt/DMA timer. 031:16 - Reserved. -