L9788 datasheet(181/264 Pages) STMICROELECTRONICS

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DS12308 Rev 4

181/264

L9788

Micro second channel (MSC) interface

263

18.2

Downstream communication

The enable input is active with inverted polarity - i.e. ‘low level' during the active phases of

command or data frames. An active enable signal validates the DI input signal. Outside the

active phase (enable line is at high level) invalid data may occur at DI. The active phase of a

downstream frame starts with the falling edge of the enable signal and ends with the rising

edge of the enable signal. The enable signal changes its state with the rising edge of the

clock CL. DI changes its state on rising edge and it is latched by L9788 on the falling edge of

CL. Downstream frames are synchronous serial frames. They support enable signal and

command/data selection bit as part of the frame. Command/data selection bit allows

distinguishing frames as command and data frames in the receiver circuit. Command

frames and data frames may be sent in any sequence with a passive phase of at least 2 CL-

cycles after each frame.

18.2.1

Command frame

A command frame always starts with a high level bit (command selection bit). The number

of the command bit of the active phase of a command frame NCB is fixed to 16. If the

number of the command bit is not equal to NCB = 16 the frame will be ignored, the

command will not be executed and the error flag (TRANS_L) will be set. If the MSC

command frame has an invalid command the flag "CMD_ERROR" is set but no action on

outputs is taken. The command frame is ignored.

The length of the command frame's passive phase tCPP must be a minimum of 2 * tCL.

VDI_low

Differential input low

detection level

VDI_low= VDI_P_low-

VDI_N_low

--100

MSC_DI_P

MSC_DI_N

VDO_L

DO output low level

VDDIO=5V or 3.3V

Isink current=2mA

0.5

MSC_DO

VDO_H

DO output high level

VDDIO =5V or 3.3V

Isink current=2mA

VDDIO

-0.5

MSC_DO

fDO

Maximum frequency

Tested by SCAN

fCK/128 fCK/64 fCK/16 MHz

MSC_DO

ENL

Low input level

-0.3

1.1

MSC_EN

ENH

High input level

2.3

VDD5

+0.3

VMSC_EN

VHYST

Hysteresis

0.1

MSC_EN

IIN

Input current

μA

MSC_EN

RPU

Pull up resistor

250

kΩ

MSC_EN

Table 86. MSC electrical characteristics (continued)

Symbol

Parameter

Test condition

Min

Typ

Max

Unit

L9788 Datasheet(PDF) 181 Page - STMicroelectronics

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