INTEGRATED CIRCUITS
SC28C94
Quad universal asynchronous
receiver/transmitter (QUART)
Product specification
1998 Aug 19
Replaces SC26C94 of 1995 May 01 and SC68C94 of 1995 May 01
IC17 Data Handbook
Philips
Semiconductors
Philips Semiconductors
Product specification
Quad universal asynchronous receiver/transmitter (QUART)
SC28C94
DESCRIPTION
The 28C94 quad universal asynchronous receiver/transmitter
(QUART) combines four enhanced Philips Semiconductors
industry-standard UARTs with an innovative interrupt scheme that
can vastly minimize host processor overhead. It is implemented
using Philips Semiconductors’ high-speed CMOS process that
combines small die size and cost with low power consumption.
The operating speed of each receiver and transmitter can be
selected independently at one of eighteen fixed baud rates, a 16X
clock derived from a programmable counter/timer, or an external 1X
or 16X clock. The baud rate generator and counter/timer can
operate directly from a crystal or from external clock inputs. The
ability to independently program the operating speed of the receiver
and transmitter make the QUART particularly attractive for
dual-speed channel applications such as clustered terminal
systems.
Each receiver is buffered with eight character FIFOs (first-in-first-out
memories) and one shift register to minimize the potential for
receiver overrun and to reduce interrupt overhead in interrupt driven
systems. In addition, a handshaking capability is provided to disable
a remote UART transmitter when the receiver buffer is full. (RTS
control)
The 28C94 provides a power-down mode in which the oscillator is
stopped and the register contents are stored. This results in reduced
power consumption on the order of several magnitudes. The
QUART is fully TTL compatible and operates from a single +5V
power supply.
PIN CONFIGURATIONS
V
CC
A5:0
CEN
RDN
WRN
D7-0
DACKN
IACKN
RQN
RESET
X1/CLK
X2
RDa-d
I/O0a–d
I/O1a–d
I/O2a–d
I/O3a–d
TDa-d
V
SS
SD00158
Figure 1. Pin Configuration
•
Programmable channel mode
•
Programmable interrupt priorities
•
Identification of highest priority interrupt
•
Global interrupt register set provides data from interrupting
channel
–
Normal (full-duplex), automatic echo, local loop back, remote
loopback
FEATURES
•
New low overhead interrupt control
•
All commercial parts meet industrial timing and temperature
parameters
•
Four Philips Semiconductors industry-standard UARTs
•
Eight byte receive FIFO and eight byte transmit FIFO for each
UART
•
Programmable data format:
–
5 to 8 data bits plus parity
–
Odd, even, no parity or force parity
–
1, 1.5 or 2 stop bits programmable in 1/16-bit increments
•
Baud rate for the receiver and transmitter selectable from:
–
23 fixed rates: 50 to 230.4K baud Non-standard rates to 1.0M
baud
–
User-defined rates from the programmable counter/timer
associated with each of two blocks
–
External 1x or 16x clock
•
Parity, framing, and overrun error detection
•
False start bit detection
•
Line break detection and generation
ORDERING INFORMATION
C G S
PACKAGES
48-Pin Plastic Dual In-Line Package (DIP)
52-Pin Plastic Leaded Chip Carrier (PLCC) Package
•
Vectored interrupts with programmable vector format
•
IACKN and programmable DTACKN signals
•
Built-in baud rate generator with choice of 18 rates
•
Four I/O pins per UART for modem controls, clocks, etc.
•
Power down mode
•
High-speed CMOS technology
•
52-pin PLCC and 48-pin DIP
•
Commercial and industrial temperature ranges available
•
On-chip crystal oscillator
•
TTL compatible
•
Single +5V power supply with low power mode
•
Two multifunction programmable 16-bit counter/timers
•
1MHz 16x mode operation
•
10ns data bus release time
•
“Watch Dog” timer for each receiver
INDUSTRIAL
V
CC
= +5V +10%,
T
A
= –40
o
C to +85
o
C
SC28C94A1N
SC28C94A1A
G
DWG #
SOT240-1
SOT238-3
1998 Aug 19
2
853–2111 19896
Philips Semiconductors
Product specification
Quad universal asynchronous receiver/transmitter (QUART)
SC28C94
PIN CONFIGURATIONS
48-Pin Dual-In-Line Package
X1/CLK
TXDD
RXDD
IRQN
A5
A4
A3
A2
A1
1
2
3
4
5
6
7
8
9
48
X2
47 V
SS
DACKN
IACKN
46
45
44
43
42
41
40
39
38
TXDB
RESET
TXDC
RXDC
I/O2D
I/O1D
I/O0D
I/O2C
I/O1C
I/O0C
RXDB
D7
8
9
52-Pin PLCC Package
RDN
CEN
V SS
VCC
WRN
A1
A2
A3
48
7
6
5
4
3
2
1
52
A0
51
50
49
47
46 A5
45 IRQN
44 RXDD
43 TXDD
42 X1/CLK
41 X2
40 V
SS
39 I/O3D
38 RESET
37 TXDC
36 RXDC
35 I/O2D
34 I/O1D
D6 10
D5 11
D4 12
D3 13
V
SS
14
D2 15
I/O3B 16
D1 17
D0 18
RXDA 19
TXDA 20
21
I/O2B
22
I/O1B
23
I/O0B
24
I/O3A
25
I/O2A
26
I/O1A
27
I/O0A
28
V SS
29
I/O0C
30
I/O1C
31 32
I/O2C
I/O3C
33
I/O0D
A0 10
WRN 11
V
SS
12
V
CC
13
CEN 14
RDN 15
DACKN 16
IACKN 17
TXDB 18
RXDB 19
D7 20
D6 21
D5 22
D4 23
D3 24
37 V
SS
36
35
34
33
32
31
30
29
28
27
26
I/O0A
I/O1A
I/O2A
I/O0B
I/O1B
I/O2B
TXDA
RXDA
D0
D1
D2
25 V
SS
A4
SD00159
Figure 2. Pin Configurations (cont.)
ABSOLUTE MAXIMUM RATINGS
1, 2
SYMBOL
T
A
T
STG
V
CC
V
S
P
D
PARAMETER
Operating ambient temperature range
3
Storage temperature range
Voltage from V
DD
to GND
4
Voltage from any pin to
ground
4
Package power dissipation (PLCC52)
Package power dissipation (PDIP48)
Derating factor above 25_C (PLCC52)
Derating factor above 25_C (PDIP48)
RATING
Note 4
–65 to +150
–0.5 to +7.0
–0.5 to V
CC
+0.5
2.8
3.1
22
25
UNIT
_C
_C
V
V
W
W
mW/_C
mW/_C
NOTES:
1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or any other condition above those indicated in the operation section of this specification is not
implied.
2. For operating at elevated temperatures, the device must be derated based on +150°C maximum junction temperature.
3. This product includes circuitry specifically designed for the protection of its internal devices from damaging effects of excessive static
charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying any voltages larger than the rated maxima.
4. Parameters are valid over specified temperature range. See ordering information table for applicable temperature range and operating
supply range.
1998 Aug 19
3
Philips Semiconductors
Product specification
Quad universal asynchronous receiver/transmitter (QUART)
SC28C94
BLOCK DIAGRAM
INTERNAL DATA
BUS
8
8
D0–D7
BUS BUFFER
CHANNEL A
8 BYTE TRANSMIT
FIFO
TxDA
TRANSMIT SHIFT
REGISTER
8 BYTE
RECEIVE FIFO
RxDA
RECEIVE SHIFT
REGISTER
MR 0, 1, 2
CR
SR
CSR Rx
CSR Tx
÷
2
X1/CLK
X2
TIMING
CRYSTAL
OSCILLATOR
POWER UP-DOWN
LOGIC
18
BAUD RATE
GENERATOR
CHANNEL B
(AS ABOVE)
INPUT PORT
CHANGE-OF-
STATE
DETECTORS (4)
IPCR
ACR
TxDB
RxDB
DUART
COMMON
AB
DUART AB
TIMING
CONTROL
RDN
WRN
CEN
A0–A5
RESET
DACKN
6
OPERATION CONTROL
ADDRESS
DECODE
R/W CONTROL
DUART CD
TXDC
TXDD
RXDC
RXDD
SAME AS
DUART AB
OUTPUT PORT
FUNCTION SELECT
LOGIC
OPCR
TIMING
CLOCK
SELECTORS
COUNTER/
TIMER
ACR
CTUR
CTLR
1:0
4
4
1:0
I/O[3:0]B
I/O[3:0]A
I/O[3:0]C
I/O[3:0]D
4
4
INTERRUPT ARBITRATION
IACKN
IRQN
•V
CC
•V
SS1
•V
SS2
•V
SS3
•V
SS4
LOGIC
GLOBAL
REGISTERS
INTERRUPT CONTROL
IMR
ISR
SD00160
Figure 3. Block Diagram
1998 Aug 19
4
Philips Semiconductors
Product specification
Quad universal asynchronous receiver/transmitter (QUART)
SC28C94
PIN DESCRIPTION
MNEMONIC
CEN
A5:0
D7:0
RDN
WRN
DACKN
TYPE
I
I
I/O
I
I
O
NAME AND FUNCTION
Chip Select:
Active low input that, in conjunction with RDN or WRN, indicates that the host MPU is trying to
access a QUART register. CEN must be inactive when IACKN is asserted.
Address Lines:
These inputs select a 28C94 register to be read or written by the host MPU.
8-bit Bidirectional Data Bus:
Used by the host MPU to read and write 28C94 registers.
Read Strobe:
Active low input. When this line is asserted simultaneously with CEN, the 28C94 places the
contents of the register selected by A5:0 on the D7:0 lines.
Write Strobe:
Active low input. When this line is asserted simultaneously with CEN, the 28C94 writes the data
on D7:0 into the register selected by A5:0.
Data ACKnowledge:
Active low, open-drain output to the host MPU, which is asserted subsequent to a read or
write operation. For a read operation, assertion of DACKN indicates that register data is valid on D7:0. For a
write operation, it indicates that the data on D7:0 has been captured into the indicated register. This signal
corresponds to READYN on 80x86 processors and DTACKN on 680x0 processors.
Interrupt Request:
This active low open-drain output to the host MPU indicating that one or more of the
enabled UART interrupt sources has reached an interrupt value which exceeds that pre-programmed by host
software. The IRQN can be used directly as a 680x0 processor input; it must be inverted for use as an 80x86
interrupt input. This signal requires an external pull-up resistor.
Interrupt ACKnowledge:
Active low input indicates host MPU is acknowledging an interrupt requested. The
28C94 responds by placing an interrupt vector or interrupt vector modified on D7-D0 and asserting DACKN. This
signal updates the CIR register in the interrupt logic. CEN must be high during this cycle.
Transmit Data:
Serial outputs from the four UARTs.
Receive Data:
Serial inputs to the four UARTs/
Input/Output 0:
A multi-use input or output signal for each UART. These pins can be used as general purpose
inputs, Clear to Send inputs, 1X or 16X Transmit Clock outputs or general purpose outputs. Change-of-state
detection is provided for these pins. I/O pins have approximately 1.5 Mohm pull–up device.
Input/Output 1:
A multi-use input or output signal for each UART. These pins can be used as general purpose
or 1X or 16X transmit clock inputs, or general purpose 1X or 16X receive clock outputs. Change-of-state
detection is provided for these pins. In addition, I/O1a and I/O1c can be used as Counter/Timer inputs and I/O1b
and I/O1d can be used as Counter/Timer outputs. I/O pins have approximately 1.5 Mohm pull–up device.
Input/Output 2:
A multi-use input or output signal for each UART. These pins can be used as general purpose
inputs, 1X or 16X receive clock inputs, general purpose outputs, RTS output or 1X or 16X receive clock outputs.
I/O pins have approximately 1.5 Mohm pull–up device.
Input/Output 3:
A multi-use input or output signal for each UART. These pins can be used as general purpose
inputs, 1X or 16X transmit clock inputs, general purpose outputs, or 1X or 16X transmit clock outputs. I/O pins
have approximately 1.5 Mohm pull–up device.
Master Reset:
Active high reset for the 28C94 logic. Must be asserted at power-up, may be asserted at other
times that the system is to be reset and restarted. OSC set to divide by 1, MR pointer set to 1, DACKN enabled,
I/O pins to input. Registers reset: MR0, OPR, CIR. IRQN, DTACKN, IVR Interrupt Vector, Power Down, Test
registers, FIFO pointers, Baud rate generator, Error Status, Watch Dog Timers, Change of State detectors,
counter/timer to timer, Transmitter and Receiver controllers and all interrupt bits. If reset pin is not used, then
first chip access should be to celar ‘power-down’ mode.
Crystal 1 or Communication Clock:
This pin is normally connected to one side of a 3.6864MHz or a
7.3728MHz crystal, or can be connected to an external clock up to 8MHz.
Crystal 2:
If a crystal is used, this pin should be connected to its other terminal. If an external clock is applied to
X1, this pin should be left unconnected.
Power and grounds:
respectively.
BLOCK A
BUS
INTERFACE
A0-A5
D (7:0)
INTERRUPT CONTROL
DTACKN
IACKN
BLOCK B
UARTS C/D
I/O CONTROL
I/O PORT CONTROL
COUNTER/TIMER
I/O PORT CONTROL
UARTS A/B
BAUD
RATE
GENERATOR
IRQN
O
IACKN
I
TDa-d
RDa-d
I/O0a-d
O
I
I/O
I/O1a-d
I/O
I/O2a-d
I/O
I/O3a-d
I/O
RESET
I
X1/CLK
X2
V
CC
, V
SS
I
O
SD00161
Figure 4. Channel Architecture
1998 Aug 19
5
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