Rainbow Electronics AT89C5122 - Manual (Page 85)

85
AT8xC5122/23
4202E–SCR–06/06
Reset Value = 0XXX X001b
Reset Value = 0111 0100b
Table 51. Smart Card ETU Register 1 - SCETU1 (S:ADh, SCRS=1)
7 6 5 4 3 2 1 0
COMP - - - - ETU10 ETU9 ETU8
Bit Number Bit Mnemonic Description
7 COMP
Compensation
Clear this bit when no time compensation is needed (i.e. when the ETU to Card CLK period ratio is close to an
integer with an error less than 1/4 of Card CLK period).
Set this bit otherwise and reduce the ETU period by 1 Card CLK cycle for even bits.
6-3 -
Reserved
The value read from these bits is indeterminate. Do not change these bits.
2-0 ETU[10:8]
ETU MSB
Used together with the ETU LSB in SCETU0 (Table 52)
Warning : the ETU counter is reloaded at each register’s write operation.
Do not change this register during character reception or transmission or while Guard Time or Waiting Time
Counters are running.
Table 52. Smart Card ETU Register 0 - SCETU0 (S:ACh, SCRS=1)
7 6 5 4 3 2 1 0
ETU7 ETU6 ETU5 ETU4 ETU3 ETU2 ETU1 ETU0
Bit Number Bit Mnemonic Description
7 - 0 ETU[7:0]
ETU LSB
The Elementary Time Unit is (ETU[10:0] - 0.5*COMP)/f, where f is the Card CLK frequency.
According to ISO 7816, ETU[10:0] can be set between 11 and 2048 (2047 ?)
The default reset value of ETU[10:0] is 372 (F=372, D=1).