MEC1322 datasheet(314/456 Pages) MICROCHIP

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MEC1322

DS00001719D-page 314

 2014 - 2015 Microchip Technology Inc.

27.10.4

HOW BIOEN BIT CONTROLS DIRECTION OF SPDOUT BUFFER

When the SPI is configured for Half Duplex mode or Dual Mode the SPDOUT pin operates as a bi-directional signal.

The BIOEN bit is used to determine the direction of the SPDOUT buffer when a byte is transmitted. Internally, the BIOEN

bit is sampled to control the direction of the SPDOUT buffer when the TX_DATA value is loaded into the transmit shift

Since the TX_DATA register may be written while a byte is being shifted out on the SPDOUT pin, the BIOEN bit does

not directly control the direction of the SPDOUT buffer. An internal DIRECTION bit, which is a latched version of the

BIOEN bit determines the direction of the SPDOUT buffer. The following list summarizes when the BIOEN bit is sam-

pled.

FIGURE 27-4:

DUAL FAST READ FLASH COMMAND

Note:

When the SPI core is used for flash commands, like the Dual Read command, the host discards the bytes

received during the command, address, and dummy byte portions of the transaction.

Rx_DATA Buffer Full (RxBF)

TX_DATA Buffer Empty (TxBE)

Write TX_Data

MCLK

BIOEN

TX_DATA

Read RX_Data

RX_DATA

Dummy Byte

BYTE 1

SPDOUT Pin

SPDIN1

SPCLKO

SPDIN2

Rx_DATA Buffer Full (RxBF)

TX_DATA Buffer Empty (TxBE)

Write TX_Data

Read RX_Data

RX_DATA

SPCLKO

SPDOUT Pin

SPDIN1

SPDIN2

Command Byte

Address [23:16]

Address Byte

[16:8]

Address Byte

[7:0]

BIOEN

TX_DATA

Comm

and

Address

23:16

Address

15:8

Address

7:0

MCLK

Dummy Byte

Byte 1

Byte 2

Byte 3

Byte 4

420

BYTE 2

BYTE 3

BYTE 4

420

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