Guard Time Counter; Figure 175. Character Frame And Compensation Mode - Holtek HT32F52342 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F52342/HT32F52352
Compensation mode
As the value of the ETUR register is obtained by the above procedure, the calculation results of the
value may not be an integer. If the calculation result is not an integer and is less than the integer
n but greater than the integer (n-1), either the integer n or (n-1) should be written into the ETUR
register depending upon whether the result is closer to integer n or (n-1). The integer n mentioned
here is a decimal.
If the calculation result is close to the value of (n-0.5), the compensation mode should be enabled by
setting the compensation enable control bit, COMP, in the ETUR register to 1 for successful data
transfer. When the result is close to the value of (n-0.5) and the compensation mode is enabled, the
value written into the ETUR register should be n. The ETU circuitry will then generate the time
unit sequence with n clock cycles and next (n-1) clock cycles alternately and so on. This results
in an average time unit of (n-0.5) clock cycles and allows a time granularity down to a half clock
cycle. Note that the ETU will reload the ETUR register value and restart counting at the time when
the Start bit appears in the SCI data Transfer Mode.
SCI_DIO
SCI_CLK
SCI_CLK
SCI_CLK

Figure 175. Character Frame and Compensation Mode

Guard Time Counter

The Guard Time Counter, GT, is a 9-bit up-counting counter which generates a minimum time
duration known as a character frame, denoted as t
characters in the SCI data transfer. The clock source of the guard time counter comes from the
ETU, named f
ETU
as the GTR register, which stores the expected value of the guard time counter. The guard time
value will be reloaded at the end of the current guard time period. Note that the guard time between
the last character received from the Smart Card and the next character transmitted by the SCI
circuitry which should be properly managed by the application program. There is no guard time
insertion when the first character is transmitted.
Rev. 1.30
Start bit
Data bits
t
ETU
Character
n n n n n
n n-1 n n-1 n
n-1 n n-1 n n-1
Note: The ETUR register value = n, i.e. 1 t
in the block diagram. There is a register related to the guard time counter known
541 of 656
Parity bit
P
n n n n n
n-1 n n-1 n n-1
n n-1 n n-1 n
=n clocks in this example.
ETU
, between the leading edges of two consecutive
GT
COMP=0
COMP=1
(Average time unit= n-0.5)
September 28, 2018