QUEUED SERIAL MODULE
M68HC16 Z SERIES
9-2
USER’S MANUAL
The SCI provides a standard non-return to zero (NRZ) mark/space format. It operates
in either full- or half-duplex mode. There are separate transmitter and receiver enable
bits and dual data buffers. A modulus-type baud rate generator provides rates from
110 baud to 781 kbaud with a 25.17 MHz system clock. Word length of either eight or
nine bits is software selectable. Optional parity generation and detection provide either
even or odd parity check capability. Advanced error detection circuitry catches glitches
of up to 1/16 of a bit time in duration. Wake-up functions allow the CPU16 to run unin-
terrupted until meaningful data is available.
9.2 QSM Registers and Address Map
There are four types of QSM registers: QSM global registers, QSM pin control regis-
ters, QSPI registers, and SCI registers. Refer to
and
9.2.2 QSM Pin Control Registers
for a discussion of global and pin control registers.
Refer to
and
for further information about
QSPI and SCI registers. Writes to unimplemented register bits have no effect, and
reads of unimplemented bits always return zero.
Refer to
for a QSM address map and register bit and field
definitions. Refer to
for more information about how the state
of MM affects the system.
9.2.1 QSM Global Registers
The QSM configuration register (QSMCR) controls the interface between the QSM
and the intermodule bus. The QSM test register (QTEST) is used during factory test
of the QSM. The QSM interrupt level register (QILR) determines the priority of inter-
rupts requested by the QSM and the vector used when an interrupt is acknowledged.
The QSM interrupt vector register (QIVR) contains the interrupt vector for both QSM
submodules. QILR and QIVR are 8-bit registers located at the same word address.
9.2.1.1 Low-Power Stop Mode Operation
When the STOP bit in QSMCR is set, the system clock input to the QSM is disabled
and the module enters low-power stop mode. QSMCR is the only register guaranteed
to be readable while STOP is asserted. The QSPI RAM is not readable in low-power
stop mode. However, writes to RAM or any register are guaranteed valid while STOP
is asserted. STOP can be set by the CPU16 and by reset.
The QSPI and SCI must be brought to an orderly stop before asserting STOP to avoid
data corruption. To accomplish this, disable QSM interrupts or set the interrupt priority
level mask in the CPU16 condition code register to a value higher than the IRQ level
requested by the QSM. The SCI receiver and transmitter should be disabled after
transfers in progress are complete. The QSPI can be halted by setting the HALT bit in
SPCR3 and then setting STOP after the HALTA flag is set. Refer to
for more information about low-power stop mode.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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