Page 47 - Embedded Microprocessor Systems Real World Design

ALE n
INTEL TIMING DATA
-RD OR -WR I

ALE n
}
MICROCHIP DATA XA x D
TIMING * WRITE CYCLE
-WR 1 I
DATA X A M D
-RD I READ CYCLE
!

ZILOG 28 -AS
FAMILY
TIMING DATA
-DS

MOTOROLA -AS 1
BBDM)
FAMILY ADDRESSBUS
TIMING
DATA BUS
-DS

HlTACHl -AS I
HE FAMILY
TIMING ADDRESS BUS
DATA BUS READ CYCLE
-RD -
)
DATA BUS -
* WRITE CYCLE
-WR J

Figure 2.2
Typical Microprocessor Bus Timing.

Figure 2.2 shows typical timing diagrams for five families of processors: Intel,
Microchip, Zilog, Motorola, and Hitachi. The speed of the signals varies greatly
from one processor to the next, but the basic waveform is the same for processors
within a given family.
The Intel timing diagram applies to Intel processors from the 8085 to the
80188/80186. It also includes the Intel microcontroller 8x3x/8x5x family of parts
when those devices are used with external memory. Other manufacturers, such as
Philips, also make variations on the 8x31 family that use Intel-type timing to access
external memory. The NEC pPD7840xx microcontroller family uses Intel timing,

32 Embedded Microprocessm Systems