SPMCK16Z4MPV20 datasheet(214/500 Pages) FREESCALE

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QUEUED SERIAL MODULE

M68HC16 Z SERIES

9-4

USER’S MANUAL

9.2.2 QSM Pin Control Registers

The QSM uses nine pins. Eight of the pins can be used for serial communication or for

parallel I/O. Clearing a bit in the port QS pin assignment register (PQSPAR) assigns

the corresponding pin to general-purpose I/O; setting a bit assigns the pin to the QSPI.

PQSPAR does not affect operation of the SCI.

The port QS data direction register (DDRQS) determines whether pins are inputs or

outputs. Clearing a bit makes the corresponding pin an input; setting a bit makes the

pin an output. DDRQS affects both QSPI function and I/O function. DDQS7 deter-

mines the direction of the TXD pin only when the SCI transmitter is disabled. When the

SCI transmitter is enabled, the TXD pin is an output.

The port QS data register (PORTQS) latches I/O data. PORTQS writes drive pins de-

fined as outputs. PORTQS reads return data present on the pins. To avoid driving un-

defined data, first write PORTQS, then configure DDRQS.

PQSPAR and DDRQS are 8-bit registers located at the same word address. Refer to

Table 9-1 for a summary of QSM pin functions.

Table 9-1 Effect of DDRQS on QSM Pin Function

QSM Pin

QSPI Mode

DDRQS Bit

Bit State

Pin Function

MISO

Master

DDQS0

Serial data input to QSPI

Disables data input

Slave

Disables data output

Serial data output from QSPI

MOSI

Master

DDQS1

Disables data output

Serial data output from QSPI

Slave

Serial data input to QSPI

Disables data input

SCK1

NOTES:

1. PQS2 is a digital I/O pin unless the SPI is enabled (SPE set in SPCR1), in which case it

becomes the QSPI serial clock SCK.

Master

DDQS2

—

Clock output from QSPI

Slave

—

Clock input to QSPI

PCS0/SS

Master

DDQS3

Assertion causes mode fault

Chip-select output

Slave

QSPI slave select input

Disables slave select input

PCS[1:3]

Master

DDQS[4:6]

Disables chip-select output

Chip-select output

Slave

Inactive

TXD2

2. PQS7 is a digital I/O pin unless the SCI transmitter is enabled (TE set in SCCR1), in

which case it becomes the SCI serial data output TXD.

—

DDQS7

Serial data output from SCI

RXD

—

None

Serial data input to SCI

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