
Single Wire Protocol Master Interface (SWPMI)
RM0351
1510/1830
DocID024597 Rev 5
44.6.2 SWPMI
Bitrate
register (SWPMI_BRR)
Address offset: 0x04
Reset value: 0x0000 0001
Bit 2
RXMODE
: Reception buffering mode
This bit is used to choose the reception buffering mode. This bit is relevant only when
TXDMA bit is set (refer to
Table 262: Buffer modes selection for transmission/reception
0: SWPMI is configured in Single software buffer mode for reception
1: SWPMI is configured in Multi software buffer mode for reception.
Note: This bit cannot be written while SWPACT bit is set.
Bit 1
TXDMA
: Transmission DMA enable
This bit is used to enable the DMA mode in transmission
0: DMA is disabled for transmission
1: DMA is enabled for transmission
Note: TXDMA is automatically cleared if the payload size of the transmitted frame is given as
0x00 (in the least significant byte of TDR for the first word of a frame). TXDMA is also
automatically cleared on underrun events (when TXUNRF flag is set in the SWP_ISR
register)
Bit 0
RXDMA
: Reception DMA enable
This bit is used to enable the DMA mode in reception
0: DMA is disabled for reception
1: DMA is enabled for reception
Table 262. Buffer modes selection for transmission/reception
Buffer mode
No software buffer
Single software buffer Multi software buffer
RXMODE/TXMODE
x
0
1
RXDMA/TXDMA
0
1
1
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
BR[5:0]
rw
rw
rw
rw
rw
rw
Bits 31:6 Reserved, must be kept at reset value
Bits 5:0
BR[5:0]
: Bitrate prescaler
This field must be programmed to set SWP bus bitrate, taking into account the F
SWPCLK
programmed in the RCC (Reset and Clock Control), according to the following formula:
F
SWP
= F
SWPCLK
/ ((BR[5:0]+1)x4)
Note: The programmed bitrate must stay within the following range: from 100 kbit/s up to
2 Mbit/s.
BR[5:0] cannot be written while SWPACT bit is set in the SWPMI_CR register.