Serial Peripheral Interface (SPI)
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This register is valid only when the SPI is configured as a master device. When the SPI is configured as a serial slave, writing to this location has
no effect; reading from this location returns 0. You cannot write to this register when SPI is busy.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RSVD
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RSVD
SER
R/W
Bit
Name
Access Reset
Description
31:1
RSVD
N/A
-
Reserved
0
SER
R/W
0
Slave Select Enable Flag. When this bit is set (1), the corresponding slave select line from the
master is activated when a serial transfer begins. It should be noted that setting or clearing bits in
this register have no effect on the corresponding slave select outputs until a transfer is started.
Before beginning a transfer, you should enable the bit in this register that corresponds to the slave
device with which the master wants to communicate.
1 – Selected
0 – Not selected
19.3.2.5
BAUDR
Name:
Baud Rate Select
Size:
16 bits
Address offset:
0x14
Read/Write access:
read/write
This register is valid only when the SPI is configured as a master device. When the SPI is configured as a serial slave, writing to this location has
no effect; reading from this location returns 0. The register derives the frequency of the serial clock that regulates the data transfer. The 16-bit
field in this register defines the ssi_clk divider value. It is impossible to write to this register when the SPI is enabled. The SPI is enabled and
disabled by writing to the SSIENR register.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RSVD
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SCKDV
R/W
Bit
Name
Access Reset
Description
31:16
RSVD
N/A
-
Reserved
15:0
SCKDV
R/W
0x0
SPI Clock Divider. The LSB for this field is always set to 0 and is unaffected by a write operation,
which ensures an even value is held in this register. If the value is 0, the serial output clock
(sclk_out) is disabled. The frequency of the sclk_out is derived from the following equation:
F
𝑠𝑐𝑙𝑘_𝑜𝑢𝑡
SCKDV
= 𝐹
𝑠𝑠𝑖_𝑐𝑙𝑘
where SCKDV is any even value between 2 and 65534.
19.3.2.6
TXFTLR
Name
: Transmit FIFO Threshold Level
Size:
6 bits
Address offset
:
0x18
Read/write access:
read/write
This register controls the threshold value for the transmit FIFO memory. It is impossible to write to this register when the SPI is enabled. The
SPI is enabled and disabled by writing to the SSIENR register.
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2019-05-15 10:08:03