Analog Integrated Circuit Device Data

Freescale Semiconductor

33

33389

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

Figure 19 illustrates content of the HC08/12 SPI Data

Register and the SBC SPI Data Register before the

transmission. The new address and R/W bits are already in

the SPI Data Register while the new data and parity bits are

still in an appropriate microcontroller register or memory. This

second byte has to be loaded into the HC08/12 SPI Data

Register after the first byte was transmitted to the SBC.

Figure 19. Microcontroller SPI Reading Data - Sequence A

After transmission of the first byte, the HC08/12 SPI read buffer contains the old address and R/W bits received from the SBC.

An appropriate operation in the microcontroller loads the new data and parity into the HC08/12 SPI Data Register (second byte).

In the SBC the internal logic loads P3-P0 and D3-D0 to the location of Bit 15 to Bit 8 in the SBC SPI Data Register, shifting this

data within the remaining eight clock cycles. Please see Figure 20.

Figure 20. Microcontroller SPI Reading Data - Sequence B

After sixteen clock cycles, the microcontrollers read buffer contains the new parity, and data and is now ready for the next

transmission. Please see Figure 21.

A5 A4 A3 A2 A1 A0

D3 D2 D1 D0

P3 P2 P1 P0

RW

RW

A3 A2 A1 A0

0

0

A5 A4

00

00

00

00

SBC SPI Data Register

Bit14 Bit13 Bit12 Bit11 Bit10 Bit9

Bit8

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Bit15

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

HC08/12 SPI Data Register

old address + R/W

old data

old parity

new address + R/W (1st byte)

new data + parity (2nd byte)

A5 A4 A3 A2 A1 A0

D3 D2 D1 D0

P3 P2 P1 P0

0

0

00

0000

00

SBC SPI Data Register

Bit14 Bit13 Bit12 Bit11 Bit10 Bit9

Bit8

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Bit15

HC08/12 SPI Data Register

new address + R/W

new data

new parity

addressed by the new address

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

A3 A2 A1 A0 RW RW

A5 A4

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

old address + R/W in

HC08/12 SPI read buffer