Programming Model
10-44
ADSP-2126x SHARC Processor Hardware Reference
If the transmit buffer remains empty, or the receive buffer remains full,
the device operates according to the states of the
SENDZ
and
GM
bits in the
SPICTLx
registers.
• If
SENDZ
= 1 and the transmit buffer is empty, the device repeatedly
transmits zeros on the
MOSI
pin. One word is transmitted for each
new transfer initiate command.
• If
SENDZ
= 0 and the transmit buffer is empty, the device repeatedly
transmits the last word transmitted before the transmit buffer
became empty.
• If
GM
= 1 and the receive buffer is full, the device continues to
receive new data from the
MISO
pin, overwriting the older data in
the
RXSPI
buffer.
• If
GM
= 0 and the receive buffer is full, the incoming data is dis-
carded, and the
RXSPI
register is not updated.
Slave Mode Core Transfers
When a device is enabled as a slave (and DMA mode is not selected), the
start of a transfer is triggered by a transition of the
SPIDS
select signal to
the active state (
LOW
) or by the first active edge of the clock (
SPICLK
),
depending on the state of
CPHASE
.
The following steps illustrate SPI operation in slave mode.
1. Write to the
SPICTLx
registers to make the mode of the serial link
the same as the mode that is set up in the SPI master.
2. Write the data to be transmitted into the
TXSPIx
registers to pre-
pare for the data transfer.
3. Once the
SPIDS
signal’s falling edge is detected, the slave starts
sending and receiving data on active
SPICLK
edges.
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...