Contents

vi

FIGURES

Figure 1.

8xC251TB/TQ Block Diagram.................................................................................................... 1

Figure 2.

The 8xC251TB/TQ Family Nomenclature .................................................................................. 2

Figure 3.

8xC251TB/TQ 44-pin PLCC Package........................................................................................ 4

Figure 4.

8xC251TB/TQ 40-pin PDIP Packages ....................................................................................... 5

Figure 5.

External Bus Cycle: Code Fetch (Nonpage Mode) .................................................................. 18

Figure 6.

External Bus Cycle: Data Read (Nonpage Mode) ................................................................... 19

Figure 7.

External Bus Cycle: Data Write (Nonpage Mode).................................................................... 20

Figure 8.

External Bus Cycle: Code Fetch (Page Mode) ........................................................................ 21

Figure 9.

External Bus Cycle: Data Read (Page Mode).......................................................................... 22

Figure 10.

External Bus Cycle: Data Write (Page Mode) .......................................................................... 23

Figure 11.

External Bus Cycle: Code Fetch/Data Read (Nonpage Mode) ................................................ 24

Figure 12.

External Bus Cycle: Data Write (Nonpage Mode).................................................................... 25

Figure 13.

External Bus Cycle: Code Fetch/Data Read (Page Mode) ...................................................... 26

Figure 14.

External Bus Cycle: Data Write (Page Mode) .......................................................................... 27

Figure 15.

Serial Port Waveform — Shift Register Mode .......................................................................... 28

Figure 16.

External Clock Drive Waveforms ............................................................................................. 29

Figure 17.

AC Testing Input, Output Waveforms....................................................................................... 29

Figure 18.

Float Waveforms ...................................................................................................................... 30

TABLES

Table 1.

Description of Product Nomenclature ........................................................................................2

Table 2.

Proliferation Options .................................................................................................................. 3

Table 3.

Package Information .................................................................................................................. 3

Table 4.

8xC251TB/TQ Pin Assignment .................................................................................................. 6

Table 5.

8xC251TB/TQ PLCC/DIP Pin Assignments Arranged by Functional Category ......................... 7

Table 6.

Signal Descriptions ....................................................................................................................8

Table 7.

Memory Signal Selections (RD1:0) ..........................................................................................10

Table 8.

8xC251TB/TQ Address Map .................................................................................................... 11

Table 9.

DC Characteristics at VCC = 4.5 – 5.5 V ..................................................................................12

Table 10.

AC Timing Symbol Definitions ..................................................................................................14

Table 11.

AC Characteristics ................................................................................................................... 14

Table 12.

Real-time Wait Timing Symbol Definitions ...............................................................................24

Table 13.

Real-Time Wait AC Timing ....................................................................................................... 27

Table 14.

Serial Port Timing — Shift Register Mode ...............................................................................28

Table 15.

External Clock Drive ................................................................................................................ 29

Table 16.

Thermal Characteristics ........................................................................................................... 30