SC26C92C1A View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'SC26C92C1A' PDF : 31 Pages View PDF
Philips Semiconductors
Dual universal asynchronous receiver/transmitter (DUART)
Product specification
SC26C92
SOPR – Set the Output Port Bits (OPR)
SOPR[7:0] – Ones in the byte written to this register will cause the
corresponding bit positions in the OPR to set to 1. Zeros have no
effect.
ROPR – Reset Output Port Bits (OPR)
ROPR[7:0] – Ones in the byte written to the ROPR will cause the
corresponding bit positions in the OPR to set to 0. Zeros have no effect.
Table 6. Bit Rate Generator Characteristics
Crystal or Clock = 3.6864MHz
NORMAL RATE
(BAUD)
ACTUAL 16X
CLOCK (kHz)
50
0.8
75
1.2
110
1.759
134.5
2.153
150
2.4
200
3.2
300
4.8
600
9.6
1050
16.756
1200
19.2
1800
28.8
2000
32.056
2400
38.4
4800
76.8
7200
115.2
9600
153.6
14.4K
230.4
19.2K
307.2
28.8K
460.8
38.4K
614.4
57.6K
921.6
115.2K
1843.2K
230.4K
3686.4K
NOTE: Duty cycle of 16X clock is 50% ± 1%.
ERROR (%)
0
0
-0.069
0.059
0
0
0
0
-0.260
0
0
0.175
0
0
0
0
0
0
0
0
0
0
0
Asynchronous UART communications can tolerate frequency error
of 4.1% to 6.7% in a “clean” communications channel. The percent
of error changes as the character length changes. The above
percentages range from 5 bits not parity to 8 bits with parity and one
stop bit. The error with 8 bits no parity and one stop bit is 4.6%. If a
stop bit length of 9/16 is used, the error tolerance will approach 0
due to a variable error of up to 1/16 bit time in receiver clock phase
alignment to the start bit.
ACR – Auxiliary Control Register
ACR[7] – Baud Rate Generator Set Select
This bit selects one of two sets of baud rates to be generated by the
BRG (see Table 5).
The selected set of rates is available for use by the Channel A and
B receivers and transmitters as described in CSRA and CSRB.
Baud rate generator characteristics are given in Table 6.
Table 7. ACR 6:4 Field Definition
ACR
6:4
MODE
CLOCK SOURCE
000 Counter
External (IP2)
001 Counter
TxCA – 1X clock of Channel A
transmitter
010 Counter
TxCB – 1X clock of Channel B
transmitter
011 Counter
Crystal or external clock
(X1/CLK) divided by 16
100 Timer (square wave) External (IP2)
101 Timer (square wave) External (IP2) divided by 16
110 Timer (square wave) Crystal or external clock
(X1/CLK)
111 Timer (square wave) Crystal or external clock
(X1/CLK) divided by 16
NOTE: The timer mode generates a squarewave.
ACR[6:4] – Counter/Timer Mode And Clock Source Select
This field selects the operating mode of the counter/timer and its
clock source as shown in Table 7.
ACR[3:0] – IP3, IP2, IP1, IP0 Change-of-State Interrupt Enable
This field selects which bits of the input port change register (IPCR)
cause the input change bit in the interrupt status register (ISR[7]) to
be set. If a bit is in the ‘on’ state the setting of the corresponding bit
in the IPCR will also result in the setting of ISR[7], which results in
the generation of an interrupt output if IMR[7] = 1. If a bit is in the
‘off’ state, the setting of that bit in the IPCR has no effect on ISR[7].
IPCR – Input Port Change Register
IPCR[7:4] – IP3, IP2, IP1, IP0 Change-of-State
These bits are set when a change-of-state, as defined in the input
port section of this data sheet, occurs at the respective input pins.
They are cleared when the IPCR is read by the CPU. A read of the
IPCR also clears ISR[7], the input change bit in the interrupt status
register. The setting of these bits can be programmed to generate
an interrupt to the CPU.
IPCR[3:0] – IP3, IP2, IP1, IP0 Change-of-State
These bits provide the current state of the respective inputs. The
information is unlatched and reflects the state of the input pins at the
time the IPCR is read.
ISR – Interrupt Status Register
This register provides the status of all potential interrupt sources.
The contents of this register are masked by the Interrupt Mask
Register (IMR). If a bit in the ISR is a ‘1’ and the corresponding bit
in the IMR is also a ‘1’, the INTRN output will be asserted (Low). If
the corresponding bit in the IMR is a zero, the state of the bit in the
ISR has no effect on the INTRN output. Note that the IMR does not
mask the reading of the ISR – the true status will be provided
regardless of the contents of the IMR. The contents of this register
are initialized to H‘00’ when the DUART is reset.
2000 Jan 31
21
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