11AA02UID

DS20005206A-page 6

 2013 Microchip Technology Inc.

3.0

BUS CHARACTERISTICS

3.1

Standby Pulse

When the master has control of SCIO, a standby pulse

this time, the 11AA02UID will reset and return to

Standby mode. Subsequently, a high-to-low transition

on SCIO (the first low pulse of the header) will return

the device to the active state.

Once a command is terminated satisfactorily (i.e., via

a NoMAK/SAK combination during the Acknowledge

sequence), performing a standby pulse is not required

to begin a new command as long as the device to be

selected is the same device selected during the previ-

observed after the end of the command and before the

in order to begin the new command.

If a command is terminated in any manner other than a

NoMAK/SAK combination, then the master must

perform a standby pulse before beginning a new

command, regardless of which device is to be selected.

An example of two consecutive commands is shown in

Figure 3-1. Note that the device address is the same

for both commands, indicating that the same device is

being selected both times.

A standby pulse cannot be generated while the slave

has control of SCIO. In this situation, the master must

wait for the slave to finish transmitting and to release

SCIO before the pulse can be generated.

If, at any point during a command an error is detected

by the master, a standby pulse should be generated

and the command should be performed again.

FIGURE 3-1:

CONSECUTIVE COMMANDS EXAMPLE

3.2

Start Data Transfer

All operations must be preceded by a start header. The

start header consists of holding SCIO low for a period

code. This code is used to synchronize the slave’s

internal clock period with the master’s clock period, so

accurate timing is very important.

When a standby pulse is not required (i.e., between

successive commands to the same device), a period of

and before the beginning of the start header.

Figure 3-2 shows the waveform for the start header,

including the required Acknowledge sequence at the

end of the byte.

FIGURE 3-2:

START HEADER

Note:

After a POR/BOR event occurs, a low-to-

high transition on SCIO must be gener-

ated before proceeding with communica-

tion, including a standby pulse.

11

0

1

0

1

00

Start Header

SCIO

Device Address

00

0

0

1

0

10

11

0

1

0

1

00

Start Header

SCIO

Device Address

00

0

0

1

0

10

Note 1: After a POR/BOR event, a low-to-high transition on SCIO is required to occur before the first

standby pulse.

SCIO

Data ‘0’ Data ‘1’ Data ‘0’ Data ‘1’ Data ‘0’ Data ‘1’ Data ‘0’ Data ‘1’

MAK

NoSAK