RFM119W/RFM119SW

Rev 1.0 | Page 15 /19

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Table 12. TWI Requirements

Parameter

Symbol

Conditions

Min

Typ

Max

Unit

Digital Input Level High

0.8

Digital Input Level Low

0.2

CLK Frequency

10

1,000

kHz

CLK High Time

500

ns

CLK Low Time

500

ns

CLK Delay Time

CLK delay time for the first falling edge of the

TWI_RST command, see Figure 20

20

15,000

ns

DATA Delay Time

The data delay time from the last CLK rising

edge of the TWI command to the time DATA

return to default state

15,000

ns

DATA Setup Time

From DATA change to CLK falling edge

20

ns

DATA Hold Time

From CLK falling edge to DATA change

200

ns

CLK

DATA

Figure 18. Two-wire Interface Timing Diagram

Once the device is powered up, TWI_RST and SOFT_RST should be issued to make sure the device works in SLEEP state

robustly. On every transmission, TWI_RST and TWI_OFF should be issued before the transmission to make sure the TWI

circuit functions correctly. TWI_RST and SOFT_RST should be issued again after the transmission for the device going back to

SLEEP state reliably till the next transmission. The operation flow with TWI is shown as the figure below.

Reset TWI 

One Transmission  Cycle 

One Transmission  Cycle 

 

 

 

(1) ‐ TWI_RST 

(2) ‐ SOFT_RST 

(1) ‐ TWI_RST 

(2) ‐ TWI_OFF 

 

TRANSMISSION 

(1) ‐ TWI_RST 

(2) ‐ SOFT_RST 

(1) ‐ TWI_RST 

(2) ‐ TWI_OFF 

 

TRANSMISSION 

(1) ‐ TWI_RST 

(2) ‐ SOFT_RST 

 

Figure 19. RFM119W/S Operation Flow with

TWI

Table 13. TWI Commands Descriptions

Command

Descriptions

Implemented by pulling the DATA pin low for 32 clock cycles and clocking in 0x8D00, 48 clock cycles in total.

It only resets the TWI circuit to make sure it functions correctly. The DATA pin cannot detect the

Rising/Falling edge to trigger transmission after this command, until the TWI_OFF command is issued.

TWI_RST

Notes:

1.

Please ensure the DATA pin is firmly pulled low during the first 32 clock cycles.

2.

When the device is configured as Transmission Enabled by DATA Pin Falling Edge, in order to issue

falling edge, which should be longer than the minimum DATA setup time 20 ns, and shorter than 15 us,