MC68376BGMAB20 Freescale Semiconductor, MC68376BGMAB20 Datasheet - Page 231

• Manufacturer Part Number: MC68376BGMAB20
• Description: IC MCU 32BIT 8K ROM 160-QFP
• Manufacturer: Freescale Semiconductor
• Series: M683xxr

Specifications of MC68376BGMAB20

• Core Processor: CPU32
• Core Size: 32-Bit
• Speed: 20MHz
• Connectivity: CAN, EBI/EMI, SCI, SPI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 18
• Program Memory Type: ROMless
• Ram Size: 7.5K x 8
• Voltage - Supply (vcc/vdd): 4.75 V ~ 5.25 V
• Data Converters: A/D 16x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 160-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

10.9.5 PWMSM Pulse-Width Registers and Comparator
10.9.6 PWMSM Coherency
10.9.7 PWMSM Interrupts
MC68336/376
USER’S MANUAL
The pulse width section of the PWMSM consists of two 16-bit pulse width registers
(PWMB1 and PWMB2) and one 16-bit comparator. PWMB2 holds the current PWM
pulse width value, and PWMB1 holds the next PWM pulse width value. The next pulse
width of the output PWM signal is established by writing a value into PWMB1. PWMB2
acts as a double buffer for PWMB1, allowing the contents of PWMB1 to be changed
at any time without affecting the pulse width of the current output signal. PWMB2 is
not user accessible. PWMB1 can be read or written at any time. The new value in
PWMB1 is transferred to PWMB2 on the next full cycle of the output or when a one is
written to the LOAD bit in PWMSIC.
The comparator continuously compares the contents of PWMB2 with the counter.
When a match occurs, the output flip-flop is cleared. This pulse width match completes
the pulse width, however, it does not affect the counter.
The PWM output pulse may be as short as one PWM counter clock period (PWMB2 =
$0001). It may be as long as one PWM clock period less than the PWM period. For
example, a pulse width equal to 65535 PWM clock periods can be obtained by setting
PWMB2 to $FFFF and PWMA2 to $0000.
Access to PWMSM registers can be accomplished with 16-bit transfers in most cases.
The PWMSM treats a 32-bit access as two 16-bit accesses, except when the access
is a write to the period and pulse width registers. A single long word write can set both
PWMA1 and PWMB1 because they occupy subsequent memory addresses. If the
write can be completed within the current PWM period, there is no visible effect on the
output signal. New values loaded into PWMA1 and PWMB1 will be transferred into
PWMA2 and PWMB2 at the start of the next period. If the write coincides with the end
of the current PWM period, the transfer of values from PWMA1 and PWMB1 into
PWMA2 and PWMB2 will be suppressed until the end of the next period. This prevents
undesired glitches on the output signal. During the period that is output before the sup-
pressed transfer completes, the current values in PWMA2 and PWMB2 are used.
The FLAG bit in PWMSIC is set when a new PWM period begins and indicates that
the period and pulse width registers (PWMA1 and PWMB1) may be updated with new
values for the next output period. The PWMSM can optionally request an interrupt
when FLAG is set. To enable interrupts, set the IL[2:0] field in PWMSIC to a non-zero
value. The CTM4 compares the CPU32 IP mask value to the priority of the requested
interrupt designated by IL[2:0] to determine whether it should contend for arbitration
priority.
During arbitration, the BIUSM provides the arbitration value specified by IARB[2:0] in
BIUMCR and IARB3 in PWMSIC. If the CTM4 wins arbitration, it responds with a vec-
tor number generated by concatenating VECT[7:6] in BIUMCR and the six low-order
bits specified by the number of the submodule requesting service. Thus, for PWMSM8
in the CTM4, the six low-order bits would be eight in decimal, or %00100 in binary.
CONFIGURABLE TIMER MODULE 4
MOTOROLA
10-15