SDEN\
SCLK
SDI
SDO
A6
A5
A4
A3
A2
A1
A0
D7
D1
D2
D3
D4
D5
D6
D0
1
7
6
5
4
3
2
8
9
15
14
13
12
11
10
16
23
22
21
20
19
18
24
17
A13
A12
A11
A10
A9
A8
A7
A14
R/W
SDEN\
SCLK
SDI
SDO
A6
A5
A4
A3
A2
A1
A0
D7
D1
D2
D3
D4
D5
D6
D0
1
7
6
5
4
3
2
8
9
15
14
13
12
11
10
16
23
22
21
20
19
18
24
17
A13
A12
A11
A10
A9
A8
A7
A14
R/W
1266
SBAU337 – May 2020
Copyright © 2020, Texas Instruments Incorporated
Appendix: SPI Interface
Appendix A
SBAU337 – May 2020
Appendix: SPI Interface
The serial port of the AFE79xx is a flexible serial interface which communicates with industry standard
microprocessors and microcontrollers. The interface provides read/write access to all registers used to
define the operating modes of the AFE79xx. It is compatible with most synchronous transfer formats and
can be configured as a 3 or 4 terminal interface through register field GLOBAL_4PIN in global register
GLOBAL0. In both configurations, SCLK is the serial interface input clock and SDEN\ is serial interface
enable. For 3 terminal configuration, SDIO is a bidirectional terminal for both data in and data out. For 4
terminal configuration, SDIO is bidirectional and SDO is data out only. Data is input into the device with
the rising edge of SCLK. Data is output from the device on the falling edge of SCLK. The SPI registers
except for global register GLOBAL0 and GLOBAL1 are reset by writing a "1" to GLOBAL_SOFT_RESET
in global register GLOBAL0.
Each read/write operation is framed by signal SDEN\ (Serial Data Enable Bar) asserted low. The first two
bytes is the instruction cycle which identifies the following data transfer cycle as read or write as well as
the 15-bit address to be accessed. The data transfer cycle consists of one byte. There are 64 pages of
registers in the AFE79xx and address 0x00h-0x1Fh are assigned for global registers in every page. The
particular register page is selected by writing "1" to the corresponding page selection bits through field
GLOBAL_PAGE_SEL in global register GLOBAL_PAGE_SEL0-GLOBAL_PAGE_SEL7 (address 0x10h-
0x15h).
Both SPI-A and SPI-B of the AFE79xx also support streaming reads/writes and broadcasting as shown
below. The address automatically increments or decrements depends on the setting of register field
GLOBAL_ASCEND. The streaming addressing formation depends on the setting of register field
GLOBAL_ADDRESSING_TYPE.
and
show the timing of a regular SPI write and
read cycle.
and
show an example of SPI streaming write and read.
and
show the timing diagram of SPI write and read.
Figure A-1. SPI Write Bus Cycle
Figure A-2. SPI Read Bus Cycle