mcf51mm256 Freescale Semiconductor, Inc, mcf51mm256 Datasheet - Page 36

• Manufacturer Part Number: mcf51mm256
• Description: 32-bit Coldfire V1 Central Processor Unit
• Manufacturer: Freescale Semiconductor, Inc

Preliminary Electrical Characteristics
3.11
A multi-function external bus interface called Mini-FlexBus is provided with basic functionality to
interface to slave-only devices up to a maximum bus frequency of
to asynchronous or synchronous devices such as external boot ROMs, flash memories, gate-array logic, or
other simple target (slave) devices with little or no additional circuitry. For asynchronous devices a simple
chip-select based interface can be used.
All processor bus timings are synchronous; that is, input setup/hold and output delay are given in respect
to the rising edge of a reference clock, MB_CLK. The MB_CLK frequency is half the internal system bus
frequency.
The following timing numbers indicate when data is latched or driven onto the external bus, relative to the
Mini-FlexBus output clock (MB_CLK). All other timing relationships can be derived from these values.
36
1
2
Num
MB1
MB2
MB3
MB4
MB5
Specification is valid for all MB_A[19:0], MB_D[7:0], MB_CS[1:0], MB_OE, MB_R/W, and MB_ALE.
Specification is valid for all MB_D[7:0].
—
Mini-FlexBus Timing Specifications
—
C
D
D
D
T
T
Frequency of Operation
Clock Period
Output Valid
Output Hold
Input Setup
Input Hold
Table 19. Mini-FlexBus AC Timing Specifications
Characteristic
25.1666 MHz
39.73
Min
1.0
22
10
—
—
25.1666
Max
. It can be directly connected
20
—
—
—
—
Freescale Semiconductor
MHz
Unit
ns
ns
ns
ns
ns
Notes
—
—
1
1
2
2