Operation

Table 22-1. QSPI Input and Output Signals and Functions

Signal Name

Hi-Z or Actively Driven

Function

 

 

 

QSPI Data Output (QSPI_Dout)

Configurable

Serial data output from QSPI

 

 

 

QSPI Data Input (QSPI_Din)

N/A

Serial data input to QSPI

 

 

 

Serial Clock (QSPI_CLK)

Actively driven

Clock output from QSPI

 

 

 

Peripheral Chip Selects (QSPI_CS[3:0])

Actively driven

Peripheral selects

 

 

 

22.3.2 Internal Bus Interface

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. The QSPI can initiate serial transfers but cannot respond to transfers initiated by other QSPI masters.

22.4 Operation

The QSPI uses a dedicated 80-Byte block of static RAM accessible both to the module and the CPU to perform queued operations. The RAM is divided into three segments as follows:

16 command control bytes (command RAM)

16 transmit data words (transfer RAM)

16 receive data words (transfer RAM)

The RAM is organized so that 1 byte of command control data, 1 word of transmit data, and 1 word of receive data comprise 1 of the 16 queue entries (0x0–0xF).

NOTE

Throughout ColdFire documentation, “word” is used consistently and exclusively to designate a 16-bit data unit. The only exceptions to this appear in discussions of serial communication modules such as QSPI that support variable-length data units. To simplify these discussions the functional unit is referred to as a ‘word’ regardless of length.

The user initiates QSPI operation by loading a queue of commands in command RAM, writing transmit data into transmit RAM, and then enabling the QSPI data transfer. The QSPI executes the queued commands and sets the completion flag in the QSPI interrupt register (QIR[SPIF]) to signal their completion. As another option, QIR[SPIFE] can be enabled to generate an interrupt.

The QSPI uses four queue pointers. The user can access three of them through fields in QSPI wrap register (QWR):

The new queue pointer, QWR[NEWQP], points to the first command in the queue.

An internal queue pointer points to the command currently being executed.

MOTOROLA

Chapter 22. Queued Serial Peripheral Interface (QSPI) Module

22-3

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Motorola MCF5281, MCF5282 user manual Operation, Internal Bus Interface, Qspi Input and Output Signals and Functions