8xC251Tx Hardware Description

4.0 EXTENDED DATA FLOAT TIMING

The Extended Data Float Timing feature seeks to provide a solution to users that may be using slower memory devices. Essentially, this feature extends the TRHDZ1 AC timing specification to accommodate slower memory devices which require a longer period of dead time between a data and address bus cycles. This feature is controlled by a bit in the Configuration byte (UCONFIG1). Bit 3 of UCONFIG1 in the 8xC251Tx is defined as EDF#. In the 8xC251Sx, Bit 3 is defined as WSB. The implications of this change are discussed below. Refer to Chapter 4 of the 8xC251SA, 8xC251SB, 8xC251SP, 8xC251SQ Embedded Microcontroller User’s Manual (272795) for details of the device configuration for the 8xC251Sx. The information in that chapter is valid for the 8xC251Tx with the exception of the change noted in this section.

4.1Summary of the Extended Data Float Timing Changes

EDF# is used to determine whether the Extended Data Float Timing is enabled. Table 12 shows the definition of UCONFIG1 for the 8xC251Tx. Only bit 3 has been redefined.

 

 

Table 12. UCONFIG1 bit definitions for the 8xC251Tx

 

 

 

 

 

Bit Number

Bit

 

 

Function

Mnemonic

 

 

 

 

 

 

 

 

7:5

-

 

Reserved for Internal or Future Use.

 

 

 

Set these bits when programming UCONFIG1

 

 

 

 

4

INTR

 

Interrupt Mode:

 

 

 

If this bit is set, interrupts push 4 bytes onto the stack (the 3 bytes of the PC

 

 

 

and PSW1). If this bit is clear, interrupts push the 2 lower bytes of the PC

 

 

 

onto the stack.

 

 

 

 

3

EDF#

 

Extended Data Float Timings:

 

 

 

When cleared, the extended data float timings are enabled. When set,

 

 

 

8xC251Sx compatible AC timings are enabled

 

 

 

 

2:1

WSB1:0#

 

External Wait State B (Region 01:):

 

 

 

WSB1#

WSB2#

 

 

 

0

0 Inserts 3 wait states for region 01:

 

 

 

0

1 Inserts 2 wait states for region 01:

 

 

 

1

0 Inserts 1 wait state for region 01:

 

 

 

1

1 Zero wait states for region 01:

 

 

 

 

 

0

EMAP

 

EPROM Map:

 

 

 

 

For devices with 16 Kbytes of on-chip code memory, clear this bit to map the

 

 

 

upper half of the on-chip code memory to region 00: (data memory). Maps

 

 

 

FF:2000H-FF:3FFFH to 00:E000H-00:FFFFH. If this bit is set, mapping does

 

 

 

not occur and the addresses in the range 00:E000H-00:FFFFH access

 

 

 

external RAM.

 

 

 

 

 

Refer to the 8xC251SA, 8xC251SB, 8xC251SP, 8xC251SQ Embedded Microcontroller User’s Manual (272795) for the AC timings specifications.

12

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Intel 8xC251TB UCONFIG1 bit definitions for the 8xC251Tx, Reserved for Internal or Future Use, Interrupt Mode, Eprom Map
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8XC251SP, 8XC251SA, 8XC251SQ, 8xC251TB, 8xC251TQ specifications

The Intel 8XC251 series of embedded microcontrollers is a family of versatile and powerful devices, designed to meet the demands of a wide range of applications. With models such as the 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP, this series offers unique features while maintaining a high level of performance and reliability.

At the heart of the 8XC251 microcontrollers is the 8051 architecture, which provides a 16-bit processor capable of executing complex instructions efficiently. This architecture not only allows for a rich instruction set but also facilitates programming in assembly language and higher-level languages like C, which are essential for developing sophisticated embedded systems.

One of the significant features of the 8XC251 family is its integrated peripherals, including timer/counters, serial communication interfaces, and interrupt systems. These peripherals enable developers to implement timing functions, data communication, and real-time processing, all of which are crucial in modern embedded applications. The 8XC251SB and 8XC251SQ models, for instance, come equipped with multiple I/O ports that allow for interfacing with other devices and systems, enhancing their functionality in various environments.

The memory architecture of the 8XC251 devices is noteworthy, featuring on-chip ROM, RAM, and EEPROM. The on-chip memory allows for fast access times, which is essential for executing programs efficiently. Moreover, the EEPROM serves as non-volatile memory, enabling the storage of configuration settings and important data that must be retained even when power is lost.

In terms of operating voltage, the 8XC251 devices are designed to operate in a wide range, typically between 4.0V and 6.0V. This flexibility makes them suitable for battery-powered applications, where energy efficiency is critical. The power management features, including reduced power modes, further enhance their suitability for portable devices.

Lastly, the 8XC251 series is supported by a wide range of development tools and resources, allowing engineers and developers to streamline the development process. This support, combined with the microcontrollers' robust features, makes the Intel 8XC251 family a reliable choice for various embedded applications, such as industrial automation, automotive systems, and consumer electronics.

Overall, the Intel 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP deliver high performance, versatility, and ease of use, making them a preferred choice for embedded system designers looking to develop efficient and effective solutions.
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