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Philips SCC2691 User Manual

Page 16

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Philips Semiconductors

Product data sheet

SCC2691

Universal asynchronous receiver/transmitter (UART)

2006 Aug 04

16

RDN

MPI

WRN

MPO

t

PS

t

PH

t

PD

SD00125

Figure 5. I/O Timing

WRN

INTERRUPT

1

OUTPUT

RDN

INTERRUPT

1

OUTPUT

V

M

t

IR

t

IR

V

OL

+0.5V

V

OL

+0.5V

V

OL

V

OL

NOTES:

1. INTRN or MPO when used as interrupt outputs.
2. The test for open drain outputs is intended to guarantee switching of the output transistor. Measurement of this response is referenced from the midpoint of the switching signal,

V

M

, to a point 0.5V above V

OL

. This point represents noise margin that assures true switching has occurred. Beyond this level, the effects of external circuitry and test environment

are pronounced and can greatly affect the resultant measurement.

SD00126

Figure 6. Interrupt Timing

X1/CLK

C/T CLK

RxC
TxC

t

CLK

t

CTC

t

Rx

t

Tx

t

CLK

t

CTC

t

Rx

t

Tx

C1

C2

Y1

X1/CLK

X2

SCC2691

Y1 = 3.6864MHz, C

L

= 20pF

C1 = C2 = 24pF

CLK

5V

470

X1

X2

N/C

TYPICAL CRYSTAL SPECIFICATION

FREQUENCY. . . . . . . . . . . . . . 2–4MHz

LOAD CAPACITANCE (C

L

). . . 20 or 32pF (typical)

TYPE OF OPERATION . . . . . .PARALLEL RESONANT, FUND. MODE

DRIVING

FROM EXTERNAL

SOURCE

50k
to
150k

SD00127

Figure 7. Clock Timing