lecture 14 dma controller & serial communications interface (uart)

Lecture 14 DMA Controller & Serial Communications Interface (UART)

Outline

Transfer Mode Extended Repeat Area Function Address Update Function Using Offset Group Scan Mode Interrupt Sources Registers Serial Communications Interface Operation in Asynchronous Mode

Overview

The RX210 Group incorporates a 4-channel direct memory access controller (DMAC) Performs data transfers without the CPU

When a DMA transfer request is generated, the DMAC transfers data stored at the transfer source address to the transfer destination address

Transfer space: 512 Mbytes 0000 0000h to 0FFF FFFFh and F000 0000h to FFFF FFFFh excluding

reserved areas Maximum transfer volume: 1M data

Maximum number of transfers in block transfer mode: 1,024 data × 1,024 blocks

Channel priority: Channel 0 > 1 > 2 > 3 (Channel 0: Highest) Transfer data

Single data: Bit length: 8, 16, 32 bits Block size: Number of data: 1 to 1,024

Power consumption reduction function: Module stop state

Transfer Mode

Normal transfer mode One data is transferred by one transfer request

A maximum of 65535 can be set as the number of transfer operations using the DMCRAL of DMACm

When these bits are set to 0000h, no specific number of transfer operations is set Performed with the transfer counter stopped (free running mode)

Setting DMCRB of DMACm is invalid in normal transfer mode A transfer end interrupt request can be generated after

completion of the specified number of transfer operations Except in free running mode

The register update operation in normal transfer mode

Transfer Mode (cont.)

The operation in normal transfer mode


Repeat transfer mode One data is transferred by one transfer request

A maximum of 1K data can be set as a total repeat transfer size using DMCRAH of the DMACm

A maximum of 1K can be set as the number of repeat transfer operations using DMCRB of the DMACm

A maximum of 1M data (1K data × 1K count of repeat transfer operations) can be set as a total data transfer size

Either the transfer source or transfer destination can be specified as a repeat area When transfer of the repeat size data is completed, the address of

the specified repeat area (DMSAR or DMDAR) returns to the transfer start address

DMA transfer can be stopped When data of the specified repeat size has all been transferred in

repeat transfer mode The repeat size end interrupt can be requested DMA transfer can be resumed by writing 1 to DTE bit in DMCNT


A transfer end interrupt request can be generated After completion of the specified number of repeat transfer

operations

The register update operation in repeat transfer mode


The operation in repeat transfer mode


Block transfer mode A single block data is transferred by one transfer request

A maximum of 1K data can be set as a total block transfer size using DMCRA of the DMACm

A maximum of 1K can be set as the number of block transfer operations using DMCRB of the DMACm

A maximum of 1M data (1K data × 1K count of block transfer operations) can be set as a total data transfer size

Either the transfer source or transfer destination can be specified as a block area When transfer of a single block data is completed, the address of

the specified block area (DMSAR or DMDAR of the DMACm) returns to the transfer start address

DMA transfer can be stopped When a single block data has all been transferred in block mode The repeat size end interrupt can be requested DMA transfer can be resumed by writing 1 to the DTE bit in DMCNT

of DMACm in the repeat size end interrupt handling


Transfer end interrupt request can be generated After completion of the specified number of block transfers

The register update operation in block transfer mode


The operation in block transfer mode

Extended Repeat Area Function

Supports a function to specify the extended repeat areas on the transfer source and destination addresses The address registers repeatedly indicate the addresses of the

specified extended repeat areas The extended repeat areas can be specified separately to the

transfer source address register (DMSAR) and transfer destination address register (DMDAR) of DMACm

The extended repeat area on the source address is specified by the SARA[4:0] bits in DMAMD of DMACm

The extended repeat area on the destination address is specified by the DARA[4:0] bits in DMAMD of DMACm

The size can be specified separately for the source and destination sides

The area which is specified as the repeat area or block area should not be specified as the extended repeat area

DMA transfer is stopped When the address register value reaches the end address of the

extended repeat area and the extended repeat area overflows

Extended Repeat Area Function (cont.)

An interrupt by an extended repeat area overflow can be requested When an overflow occurs in the extended repeat area on the

transfer source while the SARIE bit in DMINT of DMACm is set The ESIF flag in DMSTS of DMACm is set to 1 The DTE in DMCNT of DMACm is cleared to 0 to stop DMA transfer If the ESIE bit in DMINT of DMACm is set to 1, an interrupt by an

extended repeat area overflow is requested When the DARIE bit in DMINT of DMACm is set to 1

The DMDAR becomes a target to apply the function DMA transfer can be resumed by writing 1 to the DTE bit in

DMCNT of DMACm in the interrupt handling. An example of the extended repeat area operation

Eight bytes are specified as an extended repeat area By the lower three bits of DMACm.DMSAR SARA[4:0] bits in DMACm.DMAMD = 00011b

The data size is eight bits SZ[1:0] bits in DMACm.DMTMD = 00b

Extended Repeat Area Function (cont.)

Address Update Function Using Offset

The source and destination addresses can be updated by fixing, increment, decrement, or offset addition

When the offset addition is selected The offset specified by the DMA offset register (DMOFR of

DMAC0) is added to the address Every time the DMAC performs one data transfer

This function realizes a data transfer where addresses are allocated to separated areas

Offset subtraction can also be realized by setting a negative value in DMOFR of DMAC0 The negative value must be 2’s complement

Address update function using offset can be specified only for the DMAC0 channel

The address update method in each address update mode

Address Update Function Using Offset (cont.)

An example of address updating using offset addition The transfer data is 32 bits long Offset addition is set as transfer source address update mode Increment is set as transfer destination address update mode

The second and subsequent data is each read from the transfer source address obtained by adding the offset value to the previous address

The data read from the addresses at the specified intervals is written to the continuous locations on the destination

Address Update Function Using Offset (cont.)

Activation Sources

DMAC activation by software Setting the DCTG[1:0] bits in DMTMD of DMACm to 00b To start DMA transfer by software, set the DTE bit in DMCNT of

DMACm to 1 (DMA transfer is enabled) The SWREQ in DMREQ of DMACm to 1 (DMA transfer is requested) With the DMST bit in DMAST set to 1 (DMAC activation enabled)

When the DMAC is activated by software while the CLRS bit in DMREQ of DMACm is 0 The SWREQ bit in DMREQ of DMACm is cleared to 0 after data

transfer is started in response to a DMA transfer request As the DMAC is activated by software while the CLRS bit is 1

The SWREQ bit is not cleared to 0 after data transfer is started A DMA transfer request is issued again after completion of a transfer

DMAC Activation by interrupt requests from on-chip peripheral modules or external interrupt requests

Activation Sources (cont.)

The activation source can be selected separately for each channel using the DMRSRm registers (m = 0 to 3) of the ICU

Generated while the DCTG[1:0] bits in DMTMD of DMACm is set to 01b The DTE bit in DMCNT of DMACm is set to 1 (DMA transfer is

enabled) The DMST bit in DMAST is set to 1 (DMAC activation is enabled)

Another activation request cannot be accepted during the transfer of other DMAC channel or DTC When the proceeding transfer is completed, channel arbitration

is performed A DMA transfer request of the highest priority channel is accepted DMA transfer of the channel starts

When DMA transfer starts, the ACT bit in DMSTS of DMACm is set to 1 (the DMAC is in the active state)

Ending DMA Transfer

The operation for ending DMA transfer depends on the transfer end conditions When DMA transfer ends, the DTE bit in DMCNT and the ACT

flag in DMSTS of DMACm are changed from 1 to 0 Indicating that DMA transfer has ended

Transfer end by completion of specified total number of transfer operations In normal transfer mode (DMACm.DMTMD.MD[1:0] = 00b)

When the value of DMCRAL of DMACm changes from 1 to 0, DMA transfer ends on the corresponding channel

The DTE bit in DMCNT of DMACm is cleared to 0 The DTIF bit in DMSTS of DMACm is set to 1 at the same time If the DTIE bit in DMINT of DMACm is 1 at this time, a transfer end

interrupt request is issued to the CPU or the DTC In repeat transfer mode (DMACm.DMTMD.MD[1:0] = 01b)

When the value of DMCRB of DMACm changes from 1 to 0, DMA transfer ends on the corresponding channel

Ending DMA Transfer (cont.)

The DTE bit in DMCNT of DMACm is cleared to 0 The DTIF bit in DMSTS of DMACm is set to 1 at the same time If the DTIE bit in DMINT of DMACm is 1 at this time, an interrupt

request is issued to the CPU or the DTC In block transfer mode (DMACm.DMTMD.MD[1:0] = 10b)

When the value of DMCRB of DMACm changes from 1 to 0, DMA transfer ends on the corresponding channel

The DTE bit in DMCNT of DMACm is cleared to 0 The DTIF bit in DMSTS of DMACm is set to 1 at the same time If the DTIE bit in DMINT of DMACm is 1 at this time, an interrupt

request is issued to the CPU or the DTC Before sending an interrupt request from the DMAC to the CPU or

the DTC, the interrupt control register must be set.

Transfer end by repeat size end interrupt In repeat transfer mode, a repeat size end interrupt is

requested when transfer of a 1-repeat size of data is completed While the RPTIE bit in DMINT of DMACm is set to 1


When the interrupt is requested to complete DMA transfer, the DTE bit in DMCNT of DMACm is cleared to 0

The ESIF flag in DMSTS of DMACm is set to 1 If the ESIE bit in DMINT of DMACm is 1 at this time, an interrupt

request is issued to the CPU or the DTC The transfer can be resumed by writing 1 to the DTE bit in DMCNT of

DMACm A repeat size end interrupt can be requested also in block

transfer mode The interrupt is requested in the same way as in repeat transfer

mode when transfer of a 1-block size data is completed

Transfer end by interrupt on extended repeat area overflow An interrupt by an extended repeat area overflow is requested

When an overflow on the extended repeat area occurs while the extended repeat area is specified and the SARIE or DARIE bit in DMINT of DMACm is set to 1

The DMA transfer is terminated The DTE bit in DMCNT of DMACm is cleared to 0


The ESIF flag in DMSTS of DMACm is set to 1 If the ESIE bit in DMINT of DMACm is 1 at this time, an interrupt

request is issued to the CPU or the DTC Even if an interrupt by an extended repeat area overflow is

requested during a read cycle, the following write cycle is performed In block transfer mode, even if an interrupt by an extended

repeat area overflow is requested during a 1-block transfer The remaining data in the block is transferred Transfer is terminated after a block transfer

Interrupt Sources

Each DMAC channel can output an interrupt request to the CPU or the DTC After transfer in response to one request is completed When the transfer destination is the external bus or the on-chip

peripheral bus An interrupt request is generated upon completion of data

write to the write buffer not to the actual transfer destination

The relation among the interrupt sources, the interrupt status flags, and the interrupt enable bits

Interrupt Sources (cont.)

Interrupt Sources (cont.)

The different procedures are used for canceling an interrupt to restart DMA transfer

Discontinuing or terminating DMA transfer Write 0 to the DTIF bit in DMSTS of DMACm to clear a transfer

end interrupt Or to the ESIF bit in DMSTS of DMACm to clear a repeat size

interrupt and an extended repeat area overflow interrupt The DMACm remains in the stop state When starting another DMA transfer after that, set the

appropriate registers Set the DTE bit in DMCNT of DMACm to 1 (DMA transfer enabled)

Continuing DMA transfer Write 1 to the DTE bit in DMCNT of DMACm

The ESIF bit in DMSTS of DMACm is automatically cleared to 0 (interrupt source cleared)

DMA transfer is resumed

Registers

DMA Source Address Register (DMSAR)

Registers (cont.)

DMA Destination Address Register (DMDAR)

Registers (cont.)

DMA Transfer Count Register (DMCRA)

Registers (cont.)

DMA Block Transfer Count Register (DMCRB)

DMA Transfer Enable Register (DMCNT)

Registers (cont.)

DMA Transfer Mode Register (DMTMD)

Registers (cont.)

DMA Address Mode Register (DMAMD)

Registers (cont.)

DMA Offset Register (DMOFR)

DMAC Activation Request Select Register m (DMRSRm)

Registers (cont.)

DMA Software Start Register (DMREQ)

DMA Module Activation Register (DMAST)

Registers (cont.)

DMA Status Register (DMSTS)

Registers (cont.)

DMA Interrupt Setting Register (DMINT)

Serial Communications Interface

The RX210 Group has 13 independent serial communications interface (SCI) channels The SCI is configured as SCIc module (SCI0 to SCI11) and SCId

module (SCI12) The SCIc (SCI0 to SCI11) can handle both asynchronous and

clock synchronous serial communications Asynchronous serial data communications can be carried out with

standard asynchronous communications chips Such as a Universal Asynchronous Receiver/Transmitter (UART) or

Asynchronous Communications Interface Adapter (ACIA) As an extended function in asynchronous communications mode,

the SCI also supports smart card (IC card) interfaces conforming to ISO/IEC 7816-3 (standard for Identification Cards)

Single-master operation as an simple I2C bus interface and simple SPI interfaces are also supported

As well as the functions of the SCIc module, the SCId module (SCI12) supports an extended serial protocol With a structure formed from Start Frames and Information Frames

Block Diagram

Operation in Asynchronous Mode (cont.)

Example of data format in asynchronous serial communications With 8-bit data, parity, two stop bits

Any of 12 transfer formats can be selected according to the SMR setting

Clock

The SCI's transfer clock can be selected as Either an internal clock generated by the on-chip baud rate

generator or an external clock input to the SCKn pin According to the setting of CM bit in SMR and CKE[1:0] bits in SCR

When an external clock is input to the SCKn pin The clock frequency should be 16 times the bit rate (ABCS = 0) 8 times the bit rate (when ABCS in SEMR = 1) The base clock of TMR0 and TMR1 can be selected by the ACS0 bit

in SEMR of SCIn (n = 5, 6, 12) When the SCI is operated on an internal clock, the clock can be

output from the SCKn pin The frequency of the clock output is equal to the bit rate The phase is such that the rising edge of the clock is in the middle of

the transmit data

CTS and RTS Functions

The CTS function is the use of input on the CTSn# pin in transmission control Setting the SPMR.CTSE bit to 1 enables the CTS function

Placing the low level on the CTSn# pin causes transmission to start Applying the low level to the CTS# pin while transmission is in

progress does not affect transmission of the current frame

The RTS function uses the function of output on RTSn# pin A low level is output when reception becomes possible Conditions for low-level output

The value of the RE bit in the SCR is 1 Reception is not in progress There are no received data yet to be read The ORER, FER, and PER flags in the SSR are all 0

Condition for high-level output The conditions for low-level output have not been satisfied

SCI Asynchronous Mode Initialization

Before transmitting and receiving data Start by writing the initial value “00h” to SCR Whenever the operating mode or transfer format is changed,

SCR must be initialized before the change is made When the external clock is used in asynchronous mode, ensure

that the clock signal is supplied even during initialization Clearing the SCR.RE bit to 0 initializes neither the ORER, FER,

and PER flags in SSR nor RDR Switching the value of the SCR.TE bit from 1 to 0 or 0 to 1 while

the SCR.TIE bit is 1 leads to the generation of a TXI interrupt request

SCI Asynchronous Mode Initialization (cont.)

Sample SCI initialization flowchart (asynchronous mode)

Asynchronous Mode Serial Data Transmission

In serial transmission, the SCI operates as The SCI transfers data from TDR to TSR when data is written to

TDR in the TXI interrupt processing routine The TXI interrupt at the beginning of transmission is generated When the TE bit in SCR is set to 1 after the TIE bit in SCR is set to 1 Or when these two bits are set to 1 simultaneously

Transmission starts after the CTSE bit in SPMR is set to 0 (disabling the CTS function) Or a low level on CTS# pin causes data transfer from TDR to TSR If the TIE bit in SCR is 1 at this time, a TXI interrupt request is

generated Continuous transmission is obtainable by writing the next data for

transmission to TDR in the TXI interrupt processing routine before transmission of the current data for transmission is completed

When TEI interrupt requests are in use, set the SCR.TIE bit to 0 (disabling TXI requests) and the SCR.TEIE bit to 1 (enabling TEI requests) after the last of the data to be transmitted are written to the TDR from the processing routine for TXI requests

Asynchronous Mode Serial Data Transmission (cont.)

Data is sent from the TXDn pin in the order Start bit, transmit data, parity bit or multi-processor bit (may be

omitted depending on the format), and stop bit The SCI checks for updating of (writing to) TDR at the time of

stop bit output When TDR is updated, setting of the CTSE bit in SPMR to 0 (CTS

function disabled) cause the next transfer of the next data Or a low level input on the CTSn# pin Transmission from TDR to TSR and sending of the stop bit After that, serial transmission of the next frame starts

If TDR is not updated, the TEND flag in SSR is set to 1 The stop bit is sent, and then the mark state is entered in which 1 is

output If the TEIE flag in SCR is 1 at this time, a TEI interrupt request is

generated

A sample flowchart for serial transmission in asynchronous mode

Asynchronous Mode Serial Data Transmission (cont.)

Example of operation for serial transmission in asynchronous mode From the middle of transmission until transmission completion With 8-bit data, parity, one stop bit

Asynchronous Mode Serial Data Reception

In serial data reception, the SCI operates as When the value of the RE bit in SCR becomes 1

The output signal on the RTSn# pin goes to the low level When the SCI monitors the communications line

After detects a start bit, it performs internal synchronization, stores receive data in RSR, and checks the parity bit and stop bit

If an overrun error occurs, the ORER flag in SSR is set to 1 If RIE in SCR is 1 at this time, an ERI interrupt request is generated Receive data is not transferred to RDR

If a parity error is detected, the PER bit in SSR is set to 1 and receive data is transferred to RDR If RIE in SCR is 1 at this time, an ERI interrupt request is generated

If a framing error (when the stop bit is 0) is detected, the FER bit in SSR is set to 1 and receive data is transferred to RDR If RIE in SCR is 1 at this time, an ERI interrupt request is generated

When reception finishes successfully, receive data is transferred to RDR

Asynchronous Mode Serial Data Reception (cont.)

If RIE in SCR is 1 at this time, an RXI interrupt request is generated Continuous reception is enabled by reading the receive data

transferred to RDR in this RXI interrupt processing routine before reception of the next receive data is completed

Reading out the received data that have been transferred to RDR causes the RTSn# pin to output the low level

Example of SCI operation for serial reception in asynchronous mode With 8-bit data, parity, one stop bit


Example of SCI operation for serial reception in asynchronous mode With 8-bit data, parity, one stop bit When RTS function is used


If a receive error is detected, an ERI interrupt request is generated but an RXI interrupt request is not generated Data reception cannot be resumed while the receive error flag

is 1 Clear the ORER, FER, and PER bits to 0 before resuming reception

Be sure to read the RDR during overrun error processing The states of the SSR status flags and receive data handling

when a receive error is detected

Registers

Receive Shift Register (RSR) Receive Data Register (RDR)

Transmit Shift Register (TSR) Transmit Data Register (TDR)

lecture 14 dma controller & serial communications interface (uart)

Documents

transfer counter

requesteddma transfer

repeat transfer modethe

repeat areawhen transfer

repeat transfer modeone

block areawhen transfer

transfer requesta maximum

total data transfer