HC705CT4GRSSLASHD datasheet(75/152 Pages) NXP

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Synchronous Serial Interface (SSI)

SSI Registers

MC68HC705CT4 — Rev. 2.0

General Release Specification

MOTOROLA

Synchronous Serial Interface (SSI)

9.4.2 SSI Status Register

This register is located at address $001C and contains two bits. Reset

clears both of these bits.

SF — SSI Flag

This bit is set upon occurrence of the last rising clock edge and

indicates that a data transfer has taken place. If MSTR = 0 and

SIE = 0, this bit has no effect on any further transmissions and can be

ignored without problem. However, the SF flag must be clear to write

the data register, or if SIE = 1 to clear the interrupt

1 = . If MSTR = 1, the SF flag must be cleared between transfers.

The SF flag can be cleared three different ways: (1) by reading

the SSR with SF set, followed by a read or write of the serial

data register, (2) by a system reset, or, (3) by disabling the SSI.

If the SF flag is cleared before the last edge of the next byte, it

will be set again.

DCOL — Data Collision

This is a read-only status bit, which indicates that an invalid access to

the data register was made. An invalid access can be one of the

following conditions:

•

An access of the SDR register in the middle of a transfer (after the

first falling edge of SCK and before SF is set)

•

An access of the SDR register made before an access of the SSR

DCOL is cleared by reading the status register with SF set followed

by a read or write of the data register. A reset also clears this bit.

Address:

$001C

Bit 7

654321

Bit 0

Read:

DCOL

000000

Write:

Reset:

00000000

Figure 9-4. SSI Status Register (SSR)

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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