Queued Serial Multi-Channel Module
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
15-37
Delay after transfer can be used to provide a peripheral deselect interval. A delay can also be inserted
between consecutive transfers to allow serial A/D converters to complete conversion.
Adequate delay between transfers must be specified for long data streams because the QSPI requires time
to load a transmit RAM entry for transfer. Receiving devices need at least the standard delay between
successive transfers. If the IMB3 clock is operating at a slower rate, the delay between transfers must be
increased proportionately.
15.6.5.5
Transfer Length
There are two transfer length options. The user can choose a default value of eight bits, or a programmed
value from eight (0b1000) to 16 (0b0000) bits, inclusive. Reserved values (from 0b0001 to 0b0111) default
to eight bits. The programmed value must be written into the BITS field in SPCR0. The BITSE bit in each
command RAM byte determines whether the default value (BITSE = 0) or the BITS value (BITSE = 1) is
used.
15.6.5.6
Peripheral Chip Selects
Peripheral chip-select signals are used to select an external device for serial data transfer. Chip-select
signals are asserted when a command in the queue is executed. Signals are asserted at a logic level
corresponding to the value of the PCS[3:0] bits in each command byte. More than one chip-select signal
can be asserted at a time, and more than one external device can be connected to the PCS pins, provided
proper fanout is observed. PCS0 shares a pin with the slave select SS signal, which initiates slave mode
serial transfer. If SS is taken low when the QSPI is in master mode, a mode fault occurs.
To configure a peripheral chip select, set the appropriate bit in the PQSPAR, then configure the chip-select
pin as an output by setting the appropriate bit in DDRQS. The value of the bit in PORTQS that corresponds
to the chip-select pin determines the base state of the chip-select signal. If the base state is zero, chip-select
assertion must be active high (PCS bit in command RAM must be set); if base state is one, assertion must
be active low (PCS bit in command RAM must be cleared). PORTQS bits are cleared during reset. If no
new data is written to PORTQS before pin assignment and configuration as an output, the base state of
chip-select signals is zero and chip-select pins are configured for active-high operation.
15.6.5.7
Optional Enhanced Peripheral Chip Selects
The MPC561/MPC563 have an optional on-chip decoder for the peripheral chip selects. It is enabled if
any of the PCS[4:7]EN bits are enabled in the PDMCR2 register (see
). The decode translates the
normal PCS[0:3] chip selects into a 1 of 8 decode. The polarity of the new PCS outputs can be selected by
the state of the PCSV bit in the PDMCR2. See
Table 15-22. PCS Enhanced Functionality
PCS_IN[3:0]
PCS_OUT[7:0] IF PCSV = 0
PCS_OUT[7:0] IF PCSV = 1
0000
00000001
11111110
0001
00000010
11111101
0010
00000100
11111011
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...