COM20022I Ver la hoja de datos (PDF) - SMSC -> Microchip

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COM20022I

10Mbps ARCNET controller with 2Kx8 on-board RAM

SMSC -> Microchip 

EF=0

TA/RI bit

Internal Setting Pulse

nINTR pin

Tx/Rx completed

prohibition period

EF=1

Tx/Rx completed

TA/RI bit

Internal Setting Pulse

nINTR pin

FIGURE 30 - EFFECT OF THE EF BIT ON THE TA/RI BIT

The EF bit also controls the resolution of the following issues from the COM20020 Rev B:

A) Network MAP Generation

Tentative ID is used for generating the Network MAP, but it sometimes detects a non-existent node.

Every time the Tentative-ID register is written, the effect of the old Tentative-ID remains active for a

while, which results in an incorrect network map. It can be avoided by a carefully coded software

routine, but this requires the programmer to have deep knowledge of how the COM20022 works.

Duplicate-ID is mainly used for generating the Network MAP. This has the same issue as Tentative-ID.

A minor logic change clears all the remaining effects of the old Tentative-ID and the old Duplicate-ID,

when the COM20022 detects a write operation to Tentative-ID or Node-ID register. With this change,

programmers can use the Tentative-ID or Duplicate-ID for generating the network MAP without any

issues. This change is Enabled/Disabled by the EF bit.

B) Mask Register Reset

The Mask register is reset by a soft reset in the COM20020 Rev. A, but is not reset in Rev. B. The

Mask register is related to the Status and Diagnostic register, so it should be reset by a soft reset.

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