82C50A_06 Datasheet, PDF (15/25 Pages) Intersil Corporation – CMOS Asynchronous

82C50A
TABLE 5. BAUD RATES USING 2.4576MHz CRYSTAL
DESIRED
BAUD
RATE
DIVISOR USED TO
GENERATE
16 x CLOCK
PERCENT ERROR
DIFFERENCE BETWEEN
DESIRED AND ACTUAL
50
3072
-
75
2048
-
110
1396
0.026
134.5
1142
0.0007
150
1024
-
300
512
-
600
256
-
1200
128
-
1800
85
0.392
2000
77
0.260
2400
64
-
3600
43
0.775
4800
32
-
7200
21
1.587
9600
16
-
19200
8
-
38400
4
-
TABLE 6. BAUD RATES USING 3.072MHz CRYSTAL
DESIRED
BAUD
RATE
DIVISOR USED TO
GENERATE
16 x CLOCK
PERCENT ERROR
DIFFERENCE BETWEEN
DESIRED AND ACTUAL
50
3840
-
75
2560
-
110
1745
0.026
134.5
1428
0.034
150
1280
-
300
640
-
600
320
-
1200
160
-
1800
107
0.312
2000
96
-
2400
80
-
3600
53
0.628
4800
40
-
7200
27
1.23
9600
20
-
19200
10
-
38400
5
-
Reset
After powerup, the 82C50A Master Reset Schmitt trigger
input (MR) should be held high for TMRW ns to reset the
82C50A circuits to an idle mode until initialization. A high on
MR causes the following:
1. Initializes the transmitter and receiver internal clock
counters.
2. Clears the Line Status Register (LSR), except for
Transmitter Shift Register Empty (TE MT) and Transmit
Holding Register Empty (THRE), which are set. The
Modem Control Register (MCR) is also cleared. All of the
discrete lines, memory elements and miscellaneous logic
associated with these register bits are also cleared or
turned off. Divisor Latches, Receiver Buffer Register,
Transmitter Buffer Register are not effected.
Following removal of the reset condition (MR low), the
82C50A remains in the idle mode until programmed.
A hardware reset of the 82C50A sets the THRE and TEMT
status bit in the LSR. When interrupts are subsequently
enabled, an interrupt occurs due to THRE.
A summary of the effect of a Master Reset on the 82C50A is
given in Table 7.
REGISTER/SIGNAL
Interrupt Enable Register
Interrupt Identification Register
Line Control Register
MODEM Control Register
Line Status Register
MODEM Status Register
SOUT
lntrpt (RCVR Errs)
lntrpt (RCVR Data Ready)
lntrpt (THRE)
lntrpt (Modem Status Changes)
Out2
RTS
DTR
Out1
TABLE 7. 82C50A RESET OPERATIONS
RESET CONTROL
RESET
Master Reset
All Bits Low (0-3 forced and 4-7 permanent)
Master Reset
Bit 0 is High, Bits 1 and 2 Low Bits 3-7 are Permanently Low
Master Reset
All Bits Low
Master Reset
All Bits Low
Master Reset
All Bits Low, Except Bits 5 and 6 are High
Master Reset
Bit 0-3 Low Bits 4-7 Input Signal
Master Reset
High
Read LSR/MR
Low
Read RBR/MR
Low
Read lIR/Write THR/MR
Low
Read MSR/MR
Low
Master Reset
High
Master Reset
High
Master Reset
High
Master Reset
High
15
FN2958.5
August 24, 2006