31-4
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part V. The Communications Processor Module
Figure 31-2. Single-Master/Multi-Slave Configuration
To start exchanging data, the core writes the data to be sent into a buffer, conÞgures a TxBD
with TxBD[R] set, and conÞgures one or more RxBDs. The core then sets SPCOM[STR]
in the SPI command register to start sending data, which starts once the SDMA channel
loads the Tx FIFO with data.
The SPI then generates programmable clock pulses on SPICLK for each character and
simultaneously shifts Tx data out on SPIMOSI and Rx data in on SPIMISO. Received data
is written into a Rx buffer using the next available RxBD. The SPI keeps sending and
receiving characters until the whole buffer is sent or an error occurs. The CPM then clears
TxBD[R] and RxBD[E] and issues a maskable interrupt to the CPM interrupt controller
(CPIC).
When multiple TxBDs are ready, TxBD[L] determines whether the SPI keeps transmitting
without SPCOM[STR] being set again. If the current TxBD[L] is cleared, the next TxBD
is processed after data from the current buffer is sent. Typically there is no delay on
SPIMOSI between buffers. If the current TxBD[L] is set, sending stops after the current
buffer is sent. In addition, the RxBD is closed after transmission stops, even if the Rx buffer
is not full; therefore, Rx buffers need not be the same length as Tx buffers.
SPIMOSI
SPIMISO
SPICLK
SPISEL
Slave 0
SPIMISO
SPICLK
SPISEL
Slave 1
Slave 2
Master SPI
SPIMOSI
SPIMISO
SPICLK
SPISEL
SPIMOSI
The SPISEL
SPICLK
SPIMISO
SPIMOSI
MPC860
decoder can be
either internal or
external logic.
Summary of Contents for MPC860 PowerQUICC
Page 3: ...MPC860UM AD 07 98 REV 1 MPC860 PowerQUICC ª UserÕs Manual ...
Page 36: ...xxxvi MPC860 PowerQUICC UserÕs Manual MOTOROLA CONTENTS Paragraph Number Title Page Number ...
Page 78: ...I iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
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Page 114: ...3 16 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
Page 226: ...8 32 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part II PowerPC Microprocessor Module ...
Page 262: ...9 36 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part II PowerPC Microprocessor Module ...
Page 274: ...III iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part III Configuration ...
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Page 325: ...MOTOROLA Part IV Hardware Interface IV v Part IV Hardware Interface ...
Page 326: ...IV vi MPC860 PowerQUICC UserÕs Manual MOTOROLA Part IV Hardware Interface ...
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Page 632: ...21 44 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part V The Communications Processor Module ...
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Page 998: ...37 48 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part VI Debug and Test ...
Page 1016: ...A 10 MPC860 PowerQUICC UserÕs Manual MOTOROLA Appendixes ...
Page 1024: ...B 8 MPC860 PowerQUICC UserÕs Manual MOTOROLA Appendixes ...
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