C8051T610DB24 Silicon Laboratories Inc, C8051T610DB24 Datasheet - Page 161

• Manufacturer Part Number: C8051T610DB24
• Description: DAUGHTER BOARD T610 24QFN SOCKET
• Manufacturer: Silicon Laboratories Inc

Specifications of C8051T610DB24

• Module/board Type: Socket Module - QFN
• Processor To Be Evaluated: C8051T61x
• Interface Type: USB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: C8051T610DK
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 336-1507

3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not
used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of
uniquely addressing the device in 3-wire slave mode, SPI0 must be the only slave device present on the
bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit counter
that determines when a full byte has been received. The bit counter can only be reset by disabling and re-
enabling SPI0 with the SPIEN bit. Figure 24.3 shows a connection diagram between a slave device in 3-
wire slave mode and a master device.
24.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to
logic 1:
All of the following bits must be cleared by software.




24.5. Serial Clock Phase and Polarity
Four combinations of serial clock phase and polarity can be selected using the clock control bits in the
SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one of two clock phases
(edge used to latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low
clock. Both master and slave devices must be configured to use the same clock phase and polarity. SPI0
should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The
clock and data line relationships for master mode are shown in Figure 24.5. For slave mode, the clock and
data relationships are shown in Figure 24.6 and Figure 24.7. Note that CKPHA should be set to 0 on both
the master and slave SPI when communicating between two Silicon Labs C8051 devices.
The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 24.3 controls the master mode
serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured
as a master, the maximum data transfer rate (bits/sec) is one-half the system clock frequency or 12.5 MHz,
whichever is slower. When the SPI is configured as a slave, the maximum data transfer rate (bits/sec) for
full-duplex operation is 1/10 the system clock frequency, provided that the master issues SCK, NSS (in 4-
wire slave mode), and the serial input data synchronously with the slave’s system clock. If the master
issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer rate (bits/sec)
must be less than 1/10 the system clock frequency. In the special case where the master only wants to
transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the
SPI slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency.
This is provided that the master issues SCK, NSS, and the serial input data synchronously with the slave’s
system clock.
The SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This flag can
occur in all SPI0 modes.
The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted when
the transmit buffer has not been emptied to the SPI shift register. When this occurs, the write to
SPI0DAT will be ignored, and the transmit buffer will not be written.This flag can occur in all SPI0
modes.
The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master, and for
multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the MSTEN and SPIEN
bits in SPI0CN are set to logic 0 to disable SPI0 and allow another master device to access the bus.
The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave, and a
transfer is completed and the receive buffer still holds an unread byte from a previous transfer. The new
byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The
data byte which caused the overrun is lost.
Rev 1.0
C8051T610/1/2/3/4/5/6/7
161