Motorola ColdFire MCF5281 - Manual (Page 406)

Queued Serial Peripheral Interface (QSPI)
22-2 Freescale Semiconductor
22.1.2 Overview
The queued serial peripheral interface module provides a serial peripheral interface with queued transfer
capability. It allows users to queue up to 16 transfers at once, eliminating CPU intervention between
transfers. Transfer RAM in the QSPI is indirectly accessible using address and data registers.
NOTE
The GPIO module must be configured to enable the peripheral function of
the appropriate pins (refer to
Chapter 26, “General Purpose I/O Module” )
prior to configuring the QSPI module.
22.1.3 Features
Features include:
• Programmable queue to support up to 16 transfers without user intervention
— 80 bytes of data storage provided
• Supports transfer sizes of 8 to 16 bits in 1-bit increments
• Four peripheral chip-select lines for control of up to 15 devices (All chip selects may not be
available on all devices. See
Chapter 14, “Signal Descriptions,” for details on which chip-selects
are pinned-out.)
• Baud rates from 156.9 Kbps to 20 Mbps at 80 MHz internal bus frequency
• Programmable delays before and after transfers
• Programmable QSPI clock phase and polarity
• Supports wraparound mode for continuous transfers
22.1.4 Modes of Operation
Because the QSPI module only operates in master mode, the master bit in the QSPI mode register
(QMR[MSTR]) must be set for the QSPI to function properly. If the master bit is not set, QSPI activity is
indeterminate. The QSPI can initiate serial transfers but cannot respond to transfers initiated by other QSPI
masters.
22.2 External Signal Description
The module provides access to as many as 15 devices with a total of seven signals: QSPI_DOUT,
QSPI_DIN, QSPI_CLK, QSPI_CS[3:0].
Peripheral chip-select signals, QSPI_CSn, are used to select an external device as the source or destination
for serial data transfer. Signals are asserted when a command in the queue is executed. More than one
chip-select signal can be asserted simultaneously.
Although QSPI_CSn signals function as simple chip selects in most applications, up to 15 devices can be
selected by decoding them with an external 4-to-16 decoder.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3