MC68376BGMAB20 Freescale Semiconductor, MC68376BGMAB20 Datasheet - Page 102

• 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: -

5.5.1.11 Autovector Signal
5.5.2 Dynamic Bus Sizing
5-24
MOTOROLA
When the MCU completes a bus cycle with the HALT signal asserted, DATA[15:0] is
placed in a high-impedance state and bus control signals are driven inactive; the ad-
dress, function code, size, and read/write signals remain in the same state. If HALT is
still asserted once bus mastership is returned to the MCU, the address, function code,
size, and read/write signals are again driven to their previous states. The MCU does
not service interrupt requests while it is halted. Refer to 5.6.5 Bus Exception Control
Cycles for more information.
The autovector signal (AVEC) can be used to terminate external interrupt acknowl-
edge cycles. Assertion of AVEC causes the CPU32 to generate vector numbers to lo-
cate an interrupt handler routine. If AVEC is continuously asserted, autovectors are
generated for all external interrupt requests. AVEC is ignored during all other bus cy-
cles. Refer to 5.8 Interrupts for more information. AVEC for external interrupt re-
quests can also be supplied internally by chip-select logic. Refer to 5.9 Chip-Selects
for more information. The autovector function is disabled when there is an external bus
master. Refer to 5.6.6 External Bus Arbitration for more information.
The MCU dynamically interprets the port size of an addressed device during each bus
cycle, allowing operand transfers to or from 8-bit and 16-bit ports.
During an operand transfer cycle, an external device signals its port size and indicates
completion of the bus cycle to the MCU through the use of the DSACK inputs, as
shown in Table 5-11. Chip-select logic can generate data and size acknowledge sig-
nals for an external device. Refer to 5.9 Chip-Selects for more information.
If the CPU is executing an instruction that reads a long-word operand from a 16-bit
port, the MCU latches the 16 bits of valid data and then runs another bus cycle to ob-
tain the other 16 bits. The operation for an 8-bit port is similar, but requires four read
cycles. The addressed device uses the DSACK signals to indicate the port width. For
instance, a 16-bit device always returns DSACK for a 16-bit port (regardless of wheth-
er the bus cycle is a byte or word operation).
Dynamic bus sizing requires that the portion of the data bus used for a transfer to or
from a particular port size be fixed. A 16-bit port must reside on data bus bits [15:0],
and an 8-bit port must reside on data bus bits [15:8]. This minimizes the number of bus
cycles needed to transfer data and ensures that the MCU transfers valid data.
DSACK1
1
1
0
0
Table 5-11 Effect of DSACK Signals
DSACK0
SYSTEM INTEGRATION MODULE
1
0
1
0
Insert Wait States in Current Bus Cycle
Complete Cycle — Data Bus Port Size is 8 Bits
Complete Cycle — Data Bus Port Size is 16 Bits
Reserved
Result
USER’S MANUAL
MC68336/376