MICRF505

Micrel

M9999-051304

12

May 13, 2004

Programming interface timing

Figure 4 and Table 6 shows the timing specification for the 3-wire serial programming interface.

Figure 4.

Values

Symbol

Parameter

Min.

Typ.

Max.

Units

Tper

Min. period of SCLK

50

ns

Thigh

Min. high time of SCLK

20

ns

Tlow

Min. low time of SLCK

20

ns

tfall

Max. time of falling edge of SLCK

1

ms

trise

Max. time of rising edge of SLCK

1

ms

Tcsr

Min. delay from rising edge of CS to falling edge of SCLK

0

ns

Tcsf

Min. delay from falling edge of CS to rising edge of SCLK

5

ns

Twrite

Min. delay from valid IO to falling edge of SCLK during a write operation

0

ns

Tread

Min. delay from rising edge of SCLK to valid IO during a read operation

(assuming load capacitance of IO is 25 pF)

75

ns

Programming summary

• Use CS, SCLK, and IO to get access to the control

registers in MICRF505.

• SCLK is user-controlled.

• Write to the MICRF505 at positive edges (MICRF

505 reads at negative edges).

• Read from the MICRF505 at negative edges

(MICRF505 writes at positive edges).

• After power-on: Write to the complete set of control

registers

• Address field is 7 bits long. Enter msb first

• R/W bit is 1 bit long (“1” for read, “0” for write)

• Address and R/W bit together make 1 octet

• All control registers are 8 bits long. Enter/read msb

in every octet first

• Always write 8 bits to/read 8 bits from a control

register. This is the case for registers with less than

8 used programming bits as well.

• Writing: Bring CS high, write address and R/W bit

followed by the new values to fill into the addressed

control register(s) and bring CS low for loading, i.e.

activation of the new control register values

(“load_en” = 1).

• Reading: Bring CS high, write address and R/W

bit, set IO as an input, read present contents of the

addressed control register(s), bring CS low and set

IO as an output.

SCLK

CS

IO

A6 A5

RW D7

D6

D0

D1

D2

A0

trise

tfall

Tper

Tcsr

Address Register

Data Register

LOAD

Tcsl

Tlow

ThighTread

Twrite

Table 6. Timing Specification for the 3-Wire Programming Interface