Hdlc Brg Time Constant Registers - Samsung S3C2500B User Manual

HDLC CONTROLLER
8.7.8 HDLC BRG TIME CONSTANT REGISTERS (HBRGTC)
Registers
0×F010001C
HBRGTCA
0×F011001C
HBRGTCB
0×F012001C
HBRGTCC
The HDLC BRG time constant register value can be changed at any time, but the new value does not take effect
until the next time the constant is loaded into the down counter. No attempt is made to synchronize the loading of
the time constant into HBRGTC while the clock is driving the down counter. For this reason, you should first
disable the baud rate generator before loading the new time constant into the HBRGTC register.
The formula for determining the appropriate time constant for a given baud rate is shown below. The desired rate
is shown in bits per second. This formula shows how the counter decrements from N down to zero-plus-one
cycles for reloading the time constant. This value is then fed to a toggle flip-flop to generate the square wave
output.
BRGOUT1 = (MCLK2 or RXC)/(CNT0 + 1)/(16
BRGOUT2 = BRGOUT1/(1 or 16 or 32 according to CNT2 value of the HBRGTC)
31 30 29 28 27
8-46
Table 8-15. HBRGTCA and HBRGTCB Register
Address R/W
R/W
R/W
R/W
CNT1
26 25 24 23 22 21 20 19
[1:0] Time constant value for CNT2
00 = divide by 1
01 = adivide by 16
10 = divide by 32
[3:2] Time constant value for CNT1
00 = divide by 1
01 = divide by 16
[15:4] Time constant value for CNT0
Figure 8-19. HDLC BRG Time Constant Register
Description
HDLC BRG Time Constant Register
HDLC BRG Time Constant Register
HDLC BRG Time Constant Register
)
18 17 16 15 4 3
CNT0 CNT1
S3C2500B
Reset Value
0x00000000
0x00000000
0x00000000
2 1 0
CNT2