6.2 Asynchronous Mode for Smart Card Applications

The asynchronous T=0 protocol defined by ISO 7816-3 is used for compatibility with industry-standard smart card readers. Selecting this mode requires the following power-up sequence, which complies with ISO 7816-3 for a cold reset in smart card applications.

  • Power up VCC; RST, IO-SDA and CLK-SCL are low.
  • Set I/O-SDA to Receive mode.
  • Provide a clock signal to CLK-SCL.
  • RST goes high after 400 clock cycles.

The device will respond with a 64-bit ATR code, including historical bytes to indicate the memory density within the CryptoMemory® family.

The 64-bit ATR code comes from a register that contains the characters shown in Table 6-1 and Table 6-2. The historical bytes (T1, T2, T3) indicate the density of the CryptoMemory device. This register may be modified during personalization but is locked when the PER fuse is blown. Care must be taken to respect the applicable standards defining the ATR value when operating in Asynchronous mode. The CryptoMemory device will always output all 8 bytes in response to the asynchronous ATR command, regardless of the contents of the register.

Table 6-1. ATR Codes for Lower Density CryptoMemory®

Device

TS

T0

TA(1)

TB(1)

TD(1)

TA(2)

T1

T2

AT88SC0104C

$3B

$B2

$11

$00

$10

$80

$00

$01

AT88SC0204C

$3B

$B2

$11

$00

$10

$80

$00

$02

AT88SC0404C

$3B

$B2

$11

$00

$10

$80

$00

$04

AT88SC0808C

$3B

$B2

$11

$00

$10

$80

$00

$08

AT88SC1616C

$3B

$B2

$11

$00

$10

$80

$00

$16

Table 6-2. ATR Codes for Higher Density CryptoMemory®

Device

TS

T0

TA(1)

TB(1)

TD(1)

T1

T2

T3

AT88SC3216C

$3B

$B3

$11

$00

$00

$00

$00

$32

AT88SC6416C

$3B

$B3

$11

$00

$00

$00

$00

$64

AT88SC12816C

$3B

$B3

$11

$00

$00

$00

$01

$28

AT88SC25616C

$3B

$B3

$11

$00

$00

$00

$02

$56

Once Asynchronous mode has been selected, it is not possible to switch to Synchronous mode without powering off the device.
Figure 6-2. Power-Up Sequence for Smart Card Mode
???

After a successful ATR, the Protocol and Parameter Selection (PPS) protocol defined by ISO 7816-3 may be used to negotiate the communications speed with CryptoMemory devices 32 Kb and larger in user memory. CryptoMemory supports D values of 1, 2, 4, 8, 12, and 16 for an F value of 372. It also supports D values of 8 and 16 for F = 512. This allows selection of eight communication speeds ranging from 9,600 baud to 153,600 baud.

Smart card applications that support the Two-Wire protocol can also use CryptoMemory in Synchronous mode.