MCP19124 datasheet(189/236 Pages) MICROCHIP

189 / 236 page

 2016 Microchip Technology Inc.

DS20005619A-page 189

MCP19124/5

28.5.13.2

Bus Collision During a Repeated

Start Condition

During a Repeated Start condition, a bus collision

occurs if:

a) A low level is sampled on SDA when SCL goes

from low level to high level.

b) SCL goes low before SDA is asserted low,

indicating that another master is attempting to

transmit a data ‘1’.

When the user releases SDA and the pin is allowed to

float high, the BRG is loaded with SSPADD and counts

down to zero. The SCL pin is then deasserted and,

when sampled high, the SDA pin is sampled.

If SDA is low, a bus collision has occurred (i.e., another

master is attempting to transmit a data ‘0’; Figure 28-28).

If SDA is sampled high, the BRG is reloaded and begins

counting. If SDA goes from high to low before the BRG

times out, no bus collision occurs because no two

masters can assert SDA at exactly the same time.

If SCL goes from high to low before the BRG times out

and SDA has not already been asserted, a bus collision

occurs. In this case, another master is attempting to

transmit a data ‘1’ during the Repeated Start condition

(refer to Figure 28-29).

If, at the end of the BRG time-out, both SCL and SDA

are still high, the SDA pin is driven low and the BRG is

reloaded and begins counting. At the end of the count,

regardless of the status of the SCL pin, the SCL pin is

driven low and the Repeated Start condition is complete.

FIGURE 28-28:

BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)

FIGURE 28-29:

BUS COLLISION DURING A REPEATED START CONDITION (CASE 2)

SDA

SCL

RSEN

BCLIF

SSPIF

Cleared by software

‘0’

Sample SDA when SCL goes high.

If SDA = 0, set BCLIF and release SDA and SCL.

SDA

SCL

BCLIF

RSEN

SSPIF

TBRG

‘0’

SCL goes low before SDA,

set BCLIF. Release SDA and SCL.

Interrupt cleared

by software

‘0’

MCP19124 Datasheet(PDF) 189 Page - Microchip Technology

MCP19124 Datasheet(HTML) 189 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL