SCS152

© 1997 Microchip Technology Inc.

Preliminary

DS40150B-page 7

3.3

RDBIT/PUTBIT

The RDBIT command increments the internal address

counter on the leading edge of the SCK pulse and

reads the resulting bit in EEPROM. This SDIO line is

updated on the falling edge of the SCK pulse. If the new

address is in the UKEY0 area, the SDIO line will be

tri-stated immediately in preparation of transport code

entry, even if the device is in user mode. Figure 3-2

shows two consecutive RDBIT commands.

The PUTBIT command mirrors a RDBIT command, but

data is transmitted to the chip instead of transmitting

data from the chip. It also increments the internal

address counter. PUTBIT is used to enter the transport

code in issuer mode and the challenge bits, during

signature computation. Figure 3-3 shows data entry,

typically during transport code entry.

FIGURE 3-2:

RDBIT

FIGURE 3-3:

DATA ENTRY (TRANSPORT CODE DETAIL)

SCI

SCK

SDIO

IOMAP(n)

IOMAP(n-1)

SCI

SCK

SDIO

Tl

IOMAP(147)

TC(0)

TC(1)