at32uc3b0512-z2ues ATMEL Corporation, at32uc3b0512-z2ues Datasheet - Page 205

• Manufacturer Part Number: at32uc3b0512-z2ues
• Description: 32-bit Avr Microcontroller
• Manufacturer: ATMEL Corporation

18.7.3.7
Figure 18-8. Peripheral Deselection
18.7.3.8
32059J–12/2010
Write SPI_TDR
Write SPI_TDR
Write SPI_TDR
NPCS[0..3]
NPCS[0..3]
NPCS[0..3]
TDRE
TDRE
TDRE
Peripheral Deselection
Mode Fault Detection
A
A
A
When operating normally, as soon as the transfer of the last data written in TDR is completed,
the NPCS lines all rise. This might lead to runtime error if the processor is too long in responding
to an interrupt, and thus might lead to difficulties for interfacing with some serial peripherals
requiring the chip select line to remain active during a full set of transfers.
To facilitate interfacing with such devices, the Chip Select Register can be programmed with the
CSAAT bit (Chip Select Active After Transfer) at 1. This allows the chip select lines to remain in
their current state (low = active) until transfer to another peripheral is required.
Figure 18-8 on page 205
CSAAT bits.
A mode fault is detected when the SPI is programmed in Master Mode and a low level is driven
by an external master on the NPCS0/NSS signal. NPCS0, MOSI, MISO and SPCK must be con-
figured in open drain through the GPIO controller, so that external pull up resistors are needed to
guarantee high level.
DLYBCT
DLYBCT
DLYBCT
CSAAT = 0
DLYBCS
DLYBCS
DLYBCS
PCS = B
PCS=A
PCS = A
A
B
shows different peripheral deselection cases and the effect of the
A
A
A
A
DLYBCT
DLYBCT
DLYBCT
CSAAT = 1
DLYBCS
DLYBCS
PCS = B
PCS = A
A
A
PCS = A
DLYBCS
AT32UC3B
A
A
B
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