Signal Index - Motorola MC68030 User Manual

III
NOTE
In this section and in the remainder of the manual, assertion and
negation are used to specify forcing a signal to a particu lar state. In
particular, assertion and assert refer to a signal that is active or true;
negation and negate indicate a signal that is inactive or false. These
terms are used independently of the voltage level (high or low) that
they represent.
5.1 SIGNAL INDEX
5-2
The input and output signals for the MC68030 are listed in Table 5-1. Both
the names and mnemonics are shown along with brief signal descriptions.
For more detail on each signal, refer to the paragraph in this section named
for the signal and the reference in that paragraph to a description of the
related operations.
Guaranteed timing specifications for the signals listed in Table 5-1 can be
found in M68030EC/D, MC68030 Electrical Specifications ..
Table 5-1. Signal Index (Sheet 1 of 2)
Signal Name Mnemonic
Function
Function Codes FCO-FC2 3-bit function code used to identify the address space of
each bus cycle.
Address Bus AO-A31 32-bit address bus.
Data Bus 00-031 32-bit data bus used to transfer 8, 16, 24, or 32 bits of data
per bus cycle.
Size SIZO/SIZ1 Indicates the number of bytes remaining to be transferred
for this cycle. These signals, together with AO and A 1, define
the active sections of the data bus.
Operand Cycle Start OCS Identical operation to that of ECS except that OCS is asserted
only during the first bus cycle of an operand transfer.
External Cycle Start
ECS
Provides an indication that a bus cycle is beginning.
Read/Write
RiW
Defines the bus transfer as a processor read or write.
Read-Modify-Write Cycle
RMC
Provides an indicator that the current bus cycle is part of an
indivisible read-modify-write operation.
Address Strobe
AS Indicates that a valid address is on the bus.
Data Strobe
OS
Indicates that valid data is to be placed on the data bus by
an external device or has been placed on the data bus by
the MC68030.
Data Buffer Enable DBEN Provides an enable signal for external data buffers.
MC68030 USER'S MANUAL
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