Queued Serial Peripheral Interface (QSPI) Module
MCF5253 Reference Manual, Rev. 1
Freescale Semiconductor
16-5
16.3.1.1
Transmit RAM
Data to be transmitted by the QSPI is stored in the transmit RAM segment located at addresses 0x0 to 0xF.
The user normally writes 1 word into this segment for each queue command to be executed. The user
cannot read transmit RAM.
Out-bound data must be written to transmit RAM in a right-justified format. The unused bits are ignored.
The QSPI copies the data to its data serializer (shift register) for transmission. The data is transmitted most
significant bit first and remains in transmit RAM until overwritten by the user.
16.3.1.2
Receive RAM
Data received by the QSPI is stored in the receive RAM segment located at 0x10 to 0x1F in the QSPI RAM
space. The user reads this segment to retrieve data from the QSPI. Data words with less than 16 bits are
stored right-justified in the RAM. Unused bits in a receive queue entry are set to zero upon completion of
the individual queue entry.
NOTE
Throughout ColdFire documentation, ‘word’ is used consistently and
exclusively to designate a 16-bit data unit. The only exceptions to this rule
appear in the sections that detail serial communication modules such as the
QSPI that supports variable-length data units. To simplify this issue, the
functional unit is referred to as a ‘word’ regardless of length.
QWR[CPTQP] shows which queue entries have been executed. The user can query this field to determine
which locations in receive RAM contain valid data.
16.3.1.3
Command RAM
The CPU writes one byte of control information to this segment for each QSPI command to be executed.
Command RAM is write-only memory from a user’s perspective.
Command RAM consists of 16 bytes with each byte divided into two fields. The peripheral chip select
field controls the QSPI_CS signal levels for the transfer. The command control field provides transfer
options.
A maximum of 16 commands can be in the queue. Queue execution proceeds from the address in
QWR[NEWQP] through the address in QWR[ENDQP].
The QSPI executes a queue of commands defined by the control bits in each command RAM entry which
sequence the following actions:
•
chip-select pins are activated
•
data is transmitted from transmit RAM and received into the receive RAM
•
the synchronous transfer clock QSPI_CLK is generated
Before any data transfers begin, control data must be written to the command RAM, and any out-bound
data must be written to transmit RAM. Also, the queue pointers must be initialized to the first and last
entries in the command queue.
Summary of Contents for MCF5253
Page 1: ...Document Number MCF5253RM Rev 1 08 2008 MCF5253 Reference Manual...
Page 26: ...MCF5253 Reference Manual Rev 1 xxvi Freescale Semiconductor...
Page 32: ...MCF5253 Reference Manual Rev 1 xxxii Freescale Semiconductor...
Page 46: ...MCF5253 Introduction MCF5253 Reference Manual Rev 1 1 14 Freescale Semiconductor...
Page 62: ...Signal Description MCF5253 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 98: ...Instruction Cache MCF5253 Reference Manual Rev 1 5 10 Freescale Semiconductor...
Page 104: ...Static RAM SRAM MCF5253 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 128: ...Synchronous DRAM Controller Module MCF5253 Reference Manual Rev 1 7 24 Freescale Semiconductor...
Page 144: ...Bus Operation MCF5253 Reference Manual Rev 1 8 16 Freescale Semiconductor...
Page 176: ...System Integration Module SIM MCF5253 Reference Manual Rev 1 9 32 Freescale Semiconductor...
Page 198: ...Analog to Digital Converter ADC MCF5253 Reference Manual Rev 1 12 6 Freescale Semiconductor...
Page 246: ...DMA Controller MCF5253 Reference Manual Rev 1 14 18 Freescale Semiconductor...
Page 282: ...UART Modules MCF5253 Reference Manual Rev 1 15 36 Freescale Semiconductor...
Page 344: ...Audio Interface Module AIM MCF5253 Reference Manual Rev 1 17 46 Freescale Semiconductor...
Page 362: ...I2 C Modules MCF5253 Reference Manual Rev 1 18 18 Freescale Semiconductor...
Page 370: ...Boot ROM MCF5253 Reference Manual Rev 1 19 8 Freescale Semiconductor...
