GD32F20x User Manual
706
data to be received is read from the same region.
3.
Read device ID
Read device ID command is a special command, it is issued by first polling the SC bit until it
is 0, then set SC to 1. Lower 32-bit ID read is stored in EXMC_SIDL register, and the upper
32-bit ID read is stored in EXMC_SIDH register.
4.
SPI-PSRAM access timing
In SPI mode, the EXMC can communicate with the external memory through the SPI protocol,
with 4 IOs, the clock, chip-enable, an input and an output. As shown in the diagram below,
the command is first sent serially through the EXMC’s data output line, which sets the external
memory operating mode, followed by the address section which could be of various size,
depending
on EXMC’s configuration, and lastly, the read or write data. Data bytes are written
through the data output line, while read in through the input line.
The following SPI-PSRAM waveforms are configured with:
SADRBIT[4:0] = 24,
CMDBIT[1:0] = 1
Figure 25-24. SPI-PSRAM access
Data
(EXMC_D[0])
Data
(EXMC_D[1])
Clock
(EXMC_CLK)
Chip Enable
(EXMC_NEx)
Command
Data Output 1
Data Output 2
Data Input 1
Data Input 2
4-, 8- or 16-bit wide
1~26-bit wide
8-bit wide
8-bit wide
Address
5.
SQPI-PSRAM access timing
In SQPI mode, the EXMC can communicate with the external memory through the SPI
protocol in command phase, and Quad SPI protocol in address and data phase with 6 IOs,
the clock, chip-enable, and 4 bits data IO lines. As shown in the diagram below, the command
is first sent serially through the data[0] output line, which sets the external memory operating
mode, followed by the parallel address and read/write data though the 4 data IO lines.
The following SQPI-PSRAM waveforms are configured with:
ADRBIT[4:0] = 24,
CMDBIT[1:0] = 1,(can be different)
RWAITCYCLE[3:0] = WWAITCYCLE[3:0] = 2 (can be different)
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...