APPLICATION NOTE
SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
Introduction
This application note describes the operation of the DMAC, and is intended for reference to help in the design of user
software.
Target Device
SH7211
Contents
1. Introduction ....................................................................................................................................... 2
2. Description of Sample Application.................................................................................................... 3
3. Documents of Reference................................................................................................................11
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Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
1. Introduction
1.1 Specification
• DMAC channel 0 is used.
• Auto-request mode is used as the interrupt source for activating DMA transfer.
• Cycle-stealing mode is used as the bus mode.
1.2 Used Module
• Direct memory access controller (DMAC channel 0)
1.3 Applicable Conditions
• Microcontroller: SH7211
• Operating Frequency: Internal clock 160 MHz
Bus clock 40 MHz
Peripheral clock 40 MHz
• C Compiler: SuperH RISC engine family C/C++ compiler package Ver.9.01,
from Renesas Technology
SH7211 Group
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SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
2. Description of Sample Application
In this sample application, the direct memory access controller (DMAC) is set to auto request mode to transfer 512Kbtyte data stored in the on-chip RAM to another address.
2.1 Operation of Modules Used
When a DMA transfer request is made, the DMAC starts to transfer data in accordance with the priority order of
channels and continues the transfer operation until the transfer end condition is met. Transfer requests for the DMAC
are of three kinds: auto requests, external requests, and on-chip peripheral module requests. The bus mode is selectable
as burst mode or cycle-stealing mode.
For details on the DMAC, refer to the section on the direct memory access controller in the SH7211 Group Hardware
Manual.
An overview of the DMAC is given in table 1. Examples of DMA transfer in cycle-stealing mode and burst mode are
shown in figures 1 and 2, respectively. In addition, a block diagram of the DMAC is shown in figure 3.
Table 1 Overview of DMAC
Item Description
Number of channels 8 (CH0 to CH7)
Only 4 (CH0 to CH3) can receive external requests.
Address space 4 Gbytes
Length of transfer data Byte, word (2 bytes), longword (4 bytes), and 16 bytes (longword × 4)
Maximum transfer count 16,777,216 (24 bits) transfers
Address mode Single address mode and dual address mode
Transfer request External request, on-chip peripheral module request, and auto request
(SCIF: 8 sources, IIC3: two sources, A/D converter: one source, MTU2:
five sources, CMT: two sources)
Bus mode
Priority level Channel priority fixed mode and round-robin mode
Interrupt request
External request detection DREQ input low/high level detection, rising/falling edge detection
Transfer request acknowledge
signal/transfer end signal
Cycle-stealing mode (normal mode and intermittent mode) and burst
mode
An interrupt request to the CPU is made when half or all of a transfer
process is completed.
Active levels for DACK and TEND can be set independently
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SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
In the normal mode of cycle stealing, bus mastership is given to another bus master after each DMA
transfer of one transfer unit (byte, word, longword, or 16-byte unit). When a subsequent transfer
request occurs, bus mastership is obtained from the other bus master and transfer proceeds for one
transfer unit. When that transfer ends, the bus mastership is passed to another bus master. This is
repeated until the transfer end condition is satisfied.
The cycle-stealing normal mode can be used in transfer across any interval, regardless of the
requesting source, source, and destination of the transfer.
DREQ
Bus mastership returned to CPU once
Bus cycle
CPU CPU CPU DMAC DMAC DMAC DMAC CPUCPU
WriteRead WriteRead
Figure 1 DMA Transfer Example in Cycle-Stealing Normal Mode
(Dual Address, DREQ Low Level Detection)
In burst mode, once the DMAC has obtained bus mastership, it continues to perform transfer without
releasing the bus until the transfer end condition is satisfied. In external mode, however, when the DREQ
signal is being level-detected and changes to the non-active level, even if the tranfer end condition has not
been satisfied, bus mastership is passed to another bus master on completion of the DMA transfer request
for which the request has already been accepted.
DREQ
Bus cycle
CPU CPU CPU
DMAC DMAC DMAC DMAC CPUCPU
Read Write Read Write
Figure 2 DMA Transfer Example in Burst Mode (Dual Address, DREQ Low Level Detection)
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On-chip
memory
On-chip
peripheral
module
SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
DMAC module
RDMATCR_n
Iteration
control
Register
control
DMATCR_n
RSAR_n
SAR_n
DMA transfer acknowledge signal
Interrupt controller
External ROM
External RAM
External device
(memory mapped)
External device
(with acknowledge)
DREQ0 to DREQ3
DACK0 to DACK3,
TEND0, TEND1
DMA transfer
request signal
Internal bus
Peripheral bus
Bus state
controller
HEIn
DEIn
Start-up
control
Request
priority
control
Bus
interface
RDAR_n
DAR_n
CHCR_n
DMAOR
DMARS0 to DMARS3
[Legend]
RDMATCR: DMA reload transfer count register CHCR: DMA channel control register
DMATCR: DMA transfer count register DMAOR: DMA operation register
RSAR: DMA reload source address register DMARS0 to DMARS3: DMA extension resource selectors 0 to 3
SAR: DMA source address register HEIn: DMA transfer half-end interrupt request to the CPU
RDAR: DMA reload destination address register DEIn: DMA transfer end interrupt request to the CPU
DAR: DMA destination address register n: 0, 1, 2, 3, 4, 5, 6, 7
Figure 3 Block Diagram of DMAC
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SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
2.2 Operational Description of Sample Program
The settings of the DMAC for the sample program are listed in table 4. Also, the operation of the sample program is
illustrated in figure 4.
Table 4 Settings of DMAC
DMA transfer condition Auto request mode
Channel CH0
Length of transfer data 4 bytes
Maximum transfer count 128 transfers (128 × data length of 4 bytes = 512-byte data)
Address mode Dual address mode
Bus mode Cycle-stealing mode
Priority level Channel priority level fixed mode
Interrupt request Disable an interrupt request to the CPU at the end of a transfer
DMAC
SAR
DAR
[Legend]
SAR:Source address register
DAR:Destination address register
Transfer source
address
Transfer
destination
address
H'0xFFF81000
H'0xFFF82000
On-chip RAM
512-byte data
512-byte data
Figure 4 Operation of Sample Program
DMA transfer
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SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
2.3 Procedure for Setting Modules
This section describes the procedure for making initial settings when the DMAC is to be used to transfer data between
locations within the on-chip RAM. Auto request mode is used for the transfer requests.
By default, the on-chip peripheral modules of this MCU are in module standby mode. Whenever any of these modules
is to be used, be sure to take it out of module standby mode before making the initial settings. Although processing to
delete the end of DMA transfer is typically handled by interrupts, polling is used in this sample application. A
flowchart of the sample program is shown in figure 5. In addition, a flowchart of DMAC initialization is shown in
figure 6.
For details on registers, refer to the SH7211 Group Hardware Manual.
main
STB.CR2.BIT._DMAC = 0
DMAC_init
512-byte Initialization
completed?
Yes
DMAC0.CHCR.BIT.DE = 1
Transfer completed?
Yes
DMAC0.CHCR.BIT.DE = 0
[1]
[2]
No
[3]
[4]
No
[5]
[1] Cancel module standby mode
Activate the DMAC
[2] Initialize the DMAC (channel 0)
[3] Initialize the transfer destination
Clear a 512-byte area to 0
[4] Enable DMA transfer
Set DMA enable flag
[5] Perform DMA transfer end processing
Disable DMA transfer after confirmation
of the tranfer end.
END
* In this sample application, sleep processing is performed after the main routine is complete.
Figure 5 Flowchart of Sample Program
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DMAC_init
Set DMA channel control register
(CHCR_0)
Set DMA source address register
(SAR_0)
SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
[1] Disable DMA transfer
Set the DE (DMA enable) bit to 0
[1]
[2]
Disable DMA transfer
[2] Set the DMA transfer source address (SAR_0)
Specify the DMA transfer source address
[3] Set the DMA transfer destination address (DAR_0)
Specify the DMA transfer destination address
Set DMA destination address
register (DAR_0)
Set DMA transfer count register
(DMATCR_0)
Set DMA channel control register
(CHCR_0)
Set DMA operation register
(DMAOR)
END
[3]
[4]
[5]
[6]
[4] Specify the DMA transfer count (DMATCR_0)
Set the DMA transfer count to 128
[5] Set the channel control register (CHCR_0)
Set TC to B’1: transfer data for the count specified in DMATCR
Set RLD to B’0: disable the reload function
Set RS[3:0] (resource selector) to B’0100: auto request
Set DM[1:0] to B’01: increment the destination address
Set SM[1:0] to B’00: fix the source address
Set TB to B’0: cycle steal mode
Set IE to B’0: disable interrupts
[6] Set the DMA operation register (DMAOR)
Read from the AE and MNIF bits and clear them to 0
Clear the address error flag
Set the DME bit to 1 after clearing the flags
Enable DMA transfer on all the channels
Figure 6 Flowchart of Initializing DMAC
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Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
2.4 Register Settings for Sample Program
2.4.1 Clock Pulse Generator (CPG)
The settings of the clock pulse generator for the sample program are described in table 5.
Table 5 Settings of Clock Pulse Generator
Register Name Address Setting Value Description
Frequency control
register (FRQCR)
2.4.2 Standby Control Register
The settings of the standby control register for the sample program are described in table 6.
Table 6 Settings of Standby Control Register
Register Name Address Setting Value Description
Standby control
register 2 (STBCR2)
H’FFFE0010 H’1303 CKOEN = “B’1”: output clocks
STC[1:0] = “B’00”: frequency multiplication
ratio of PLL circuit × 1
IFC[2:0] = “B’000”: internal clock × 1
PFC[2:0] = “B’011”: peripheral clock × 1/4
H’FFFE0018 H’00 MSTP8 = “B’0”: the DMAC operates
SH7211 Group
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Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
2.4.3 Direct Memory Access Controller (DMAC)
The settings of DMAC registers for the sample program are described in table 7.
Table 7 Settings of DMAC Registers
Register Name Address Setting Value Description
DMA source address
register 0 (SAR)
DMA destination address
register 0 (DAR)
DMA transfer count
register 0 (DMATCR)
DMA channel control
register 0 (CHCR)
DMA operation register
(DMAOR)
H’FFFE1000 H’FFF81000 Transfer source start address
H’FFFE1004 H’FFF82000 Transfer destination start address
H’FFFE1008 D’128 DMA transfer count:
128 transfers
H’FFFE100C
H’FFFE1200 H’0000 0001
H’0000 0000 Before DMA initialization
DE = “B’0”: disables DMA transfer
H’8000 4410 DMA initialization
TC = “B’1”: transfers data for the count
specified in DMATCR for each transfer
request
DM[1:0] = “B’01”: increments the destination
address
SM[1:0] = “B’00”: fixes the source address
RS[3:0] = “B’0100”: auto request
TB = “B’0”: cycle-stealing mode
TS[1:0] = “B’10”: longword (4 bytes) unit
IE = “B’0”: disables interrupt requests
DE = “B’0”: disables DMA transfer
H’8000 4411 When enabling DMA transfer
DE = “B’1”: enables DMA transfer
H’8000 4410 When disabling DMA transfer
DE = “B’0”: disables DMA transfer
DME = “B’1”: enables DMA transfer on all the
channels
SH7211 Group
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Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
3. Documents for Reference
• Software Manual
SH-2A, SH2A-FPU Software Manual
The most up-to-date version of this document is available on the Renesas Technology Website.
• Hardware Manual
SH7211 Group Hardware Manual
The most up-to-date version of this document is available on the Renesas Technology Website.
SH7211 Group
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Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
Website and Support
Renesas Technology Website
http://www.renesas.com/
Inquiries
http://www.renesas.com/inquiry
csc@renesas.com
Revision Record
Description
Rev. Date
1.00 Mar.21.08 — First edition issued
All trademarks and registered trademarks are the property of their respective owners.
Page Summary
SH7211 Group
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SH7211 Group
Data Transfer between On-chip RAM Areas with DMAC (Cycle-Stealing Mode)
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