MC68376BGMAB20 Freescale Semiconductor, MC68376BGMAB20 Datasheet - Page 103

• 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: -

5.5.3 Operand Alignment
5.5.4 Misaligned Operands
MC68336/376
USER’S MANUAL
The MCU always attempts to transfer the maximum amount of data on all bus cycles.
For any bus access, it is assumed that the port is 16 bits wide when the bus cycle
begins.
Operand bytes are designated as shown in Figure 5-9. OP[0:3] represent the order of
access. For instance, OP0 is the most significant byte of a long-word operand, and is
accessed first, while OP3, the least significant byte, is accessed last. The two bytes of
a word-length operand are OP0 (most significant) and OP1. The single byte of a byte-
length operand is OP0.
The EBI data multiplexer establishes the necessary connections for different combi-
nations of address and data sizes. The multiplexer takes the two bytes of the 16-bit
bus and routes them to their required positions. Positioning of bytes is determined by
the size and address outputs. SIZ1 and SIZ0 indicate the number of bytes remaining
to be transferred during the current bus cycle. The number of bytes transferred is equal
to or less than the size indicated by SIZ1 and SIZ0, depending on port width.
ADDR0 also affects the operation of the data multiplexer. During an operand transfer,
ADDR[23:1] indicate the word base address of the portion of the operand to be ac-
cessed. ADDR0 indicates the byte offset from the base.
The CPU32 uses a basic operand size of 16 bits. An operand is misaligned when it
overlaps a word boundary. This is determined by the value of ADDR0. When ADDR0
= 0 (an even address), the address is on a word and byte boundary. When ADDR0 =
1 (an odd address), the address is on a byte boundary only. A byte operand is aligned
at any address; a word or long-word operand is misaligned at an odd address. The
CPU32 does not support misaligned transfers.
The largest amount of data that can be transferred by a single bus cycle is an aligned
word. If the MCU transfers a long-word operand through a 16-bit port, the most signif-
icant operand word is transferred on the first bus cycle and the least significant oper-
and word is transferred on a following bus cycle.
OPERAND
LONG WORD
THREE BYTE
WORD
BYTE
31
OP0
Figure 5-9 Operand Byte Order
SYSTEM INTEGRATION MODULE
24
23
OP1
OP0
BYTE ORDER
16 15
OP2
OP1
OP0
8 7
OP3
OP2
OP1
OP0
MOTOROLA
OPERAND BYTE ORDER
0
5-25