GD32F20x User Manual
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interface between MCU and SDRAM memory. It translates AHB transactions into the
appropriate SDRAM protocol, and meanwhile, makes sure the access timing requirements of
the external SDRAM devices are satisfied by the configuration of EXMC_SDTCFG register.
SDRAMC could be divided into 4 sub-modules, the read/write split, control registers, finite
state machine, and signal generator. Two pairs of FIFO is implemented to increase memory
access efficiency, one pair for write address and data, the other pair for read address and
data. SDRAMC’s block diagram is shown as follows.
Figure 25-29. SDRAM controller block diagram
RW SPLIT
ACTIVE
CACHE
pre_req
pre_ok
ack_req
ack_ok
rw_req
rw_ok
SIGNAL
GENERATOR
SDNE[1:0]
D[31:0]
NBL[3:0]
AHBS_IF_MEM
WADDR
FIFO
WDATA
FIFO
RADDR
FIFO
RDATA
FIFO
REFRESH
TIMER
AHBS_IF_REG
SDRAMC
REGS
cm_req
COMMAND
TIMERS
EXTERNAL
SDRAM
COMMAND MODE
FSM
cm_ok
command mode
request
ADDRESS
DECODE
ref_req
ref_ok
SDCK
GENERATOR
The Signal Generator handles requests from Command mode FSM, Refresh Timer and the
RW split module.
The command timers are composed by timing counters which take case the timing
specification of the SDRAM protocol.
SDRAM commands are issued by the SDRAM controller interface in the following pattern.
Table 25-21. SDRAM command truth table
SD
NE
NR
AS
NC
AS
SD
NW
E
A[n]
A[10]
A[m]
Command
H
X
X
X
X
X
X
Command inhibit (No operation)
L
H
H
H
X
X
X
No operation
L
H
H
L
X
X
X
Burst Terminate
L
H
L
H
Bank
L
Col
Burst read from current row
L
H
L
H
Bank
H
Col
Burst read from current row, precharge when
done
Содержание GD32F20 Series
Страница 1: ...GigaDevice Semiconductor Inc GD32F20x ARM Cortex M3 32 bit MCU User Manual Revision 2 2 Oct 2019 ...
Страница 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Страница 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Страница 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
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Страница 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...