MC68HC000RC8 Freescale Semiconductor, MC68HC000RC8 Datasheet - Page 39

• Manufacturer Part Number: MC68HC000RC8
• Description: IC MPU 32BIT 8MHZ 68-PGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68HC000RC8

• Processor Type: M680x0 32-Bit
• Speed: 8MHz
• Voltage: 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 68-PGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

SECTION 4
8-BIT BUS OPERATION
The following paragraphs describe control signal and bus operation for 8-bit operation
during data transfer operations, bus arbitration, bus error and halt conditions, and reset
operation. The 8-bit bus operations devices are the MC68008, MC68HC001 in 8-bit mode,
and MC68EC000 in 8-bit mode. The MC68HC001 and MC68EC000 select 8-bit mode by
grounding mode during reset.
4.1 DATA TRANSFER OPERATIONS
Transfer of data between devices involves the following signals:
The address and data buses are separate parallel buses used to transfer data using an
asynchronous bus structure. In all cases, the bus master must deskew all signals it issues
at both the start and end of a bus cycle. In addition, the bus master must deskew the
acknowledge and data signals from the slave device. For the MC68HC001 and
MC68EC000, UDS is held negated and D15–D8 are undefined in 8-bit mode.
The following paragraphs describe the read, write, read-modify-write, and CPU space
cycles. The indivisible read-modify-write cycle implements interlocked multiprocessor
communications. A CPU space cycle is a special processor cycle.
4.1.1 Read Cycle
During a read cycle, the processor receives one byte of data from the memory or from a
peripheral device. When the data is received, the processor internally positions the byte
appropriately.
The 8-bit operation must perform two or four read cycles to access a word or long word,
asserting the data strobe to read a single byte during each cycle. The address bus in 8-bit
operation includes A0, which selects the appropriate byte for each read cycle. Figure 4-1
and 4-2 illustrate the byte read-cycle operation.
MOTOROLA
1. Address bus A0 through highest numbered address line
2. Data bus D0 through D7
3. Control signals
M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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