Control Registers
1150
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Multi-Buffered Serial Peripheral Interface Module (MibSPI) with Parallel Pin
Option (MibSPIP)
24.9.2 SPI Global Control Register 1 (SPIGCR1)
Figure 24-27. SPI Global Control Register 1 (SPIGCR1) [offset = 04h]
31
25
24
23
17
16
Reserved
SPIEN
Reserved
LOOPBACK
R-0
R/W-0
R-0
R/WP-0
15
9
8
7
2
1
0
Reserved
POWERDOWN
Reserved
CLKMOD
MASTER
R-0
R/W-0
R-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; WP = Write in privilege mode only; -
n
= value after reset
Table 24-9. SPI Global Control Register 1 (SPIGCR1) Field Descriptions
Bit
Field
Value
Description
31-25
Reserved
0
Reads return 0. Writes have no effect.
24
SPIEN
SPI enable. This bit enables SPI transfers. This bit must be set to 1 after all other SPI
configuration bits have been written. When the SPIEN bit is 0 or cleared to 0, the following SPI
registers get forced to their default states:
• Both TX and RX shift registers
• The TXDATA fields of the SPI Transmit Data Register 0 (SPIDAT0) and the SPI Transmit
Data Register 1 (SPIDAT1)
• All the fields of the SPI Flag Register (SPIFLG)
• Contents of SPIBUF and the internal RXBUF registers
0
The SPI is not activated for transfers.
1
Activates SPI.
23-17
Reserved
0
Reads return 0. Writes have no effect.
16
LOOPBACK
Internal loop-back test mode. The internal self-test option can be enabled by setting this bit. If
the SPISIMO and SPISOMI pins are configured with SPI functionality, then the SPISIMO[7:0]
pins are internally connected to the SPISOMI[7:0] pins (transmit data is looped back as receive
data). GIO mode for these pins is not supported in loopback mode. Externally, during loop-back
operation, the SPICLK pin outputs an inactive value and SPISOMI[7:0] remains in the high-
impedance state. If the SPI is initialized in slave mode or a data transfer is ongoing, errors may
result.
Note: This loopback mode can only be used in master mode. Master mode must be
selected before setting LOOPBACK. When this mode is selected, the CLKMOD bit should
be set to 1, meaning that SPICLK is internally generated.
0
Internal loop-back test mode is disabled.
1
Internal loop-back test mode is enabled.
15-9
Reserved
0
Reads return 0. Writes have no effect.
8
POWERDOWN
When active, the SPI state machine enters a power-down state.
0
The SPI is in active mode.
1
The SPI is in power-down mode.
7-2
Reserved
0
Reads return 0. Writes have no effect.
1
CLKMOD
Clock mode. This bit selects either an internal or external clock source. This bit also determines
the I/O direction of the SPIENA and SPICS pins in functional mode.
0
Clock is external.
• SPIENA is an output.
• SPICS are inputs.
1
Clock is internally-generated.
• SPIENA is an input.
• SPICS are outputs.