UPI-C42 UPI-L42
4
P
24
and P
25
are port pins or Buffer Flag pins
which can be used to interrupt a master proces-
sor These pins default to port pins on Reset
If the ‘‘EN FLAGS’’ instruction has been execut-
ed P
24
becomes the OBF (Output Buffer Full)
pin A ‘‘1’’ written to P
24
enables the OBF pin (the
pin outputs the OBF Status Bit) A ‘‘0’’ written to
P
24
disables the OBF pin (the pin remains low)
This pin can be used to indicate that valid data is
available from the UPI (in Output Data Bus Buff-
er)
If ‘‘EN FLAGS’’ has been executed P
25
be-
comes the IBF (Input Buffer Full) pin A ‘‘1’’ writ-
ten to P
25
enables the IBF pin (the pin outputs
the inverse of the IBF Status Bit A ‘‘0’’ written to
P
25
disables the IBF pin (the pin remains low)
This pin can be used to indicate that the UPI is
ready for data
Data Bus Buffer Interrupt Capability
UPI-42 COMPATIBLE FEATURES
1
Two Data Bus Buffers one for input and one for
output This allows a much cleaner Master Slave
protocol
290414 –5
2
8 Bits of Status
ST
7
ST
6
ST
5
ST
4
F
1
F
0
IBF OBF
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
ST
4
– ST
7
are user definable status bits These
bits are defined by the ‘‘MOV STS A’’ single
byte single cycle instruction Bits 4–7 of the
acccumulator are moved to bits 4– 7 of the status
register Bits 0 – 3 of the status register are not
affected
MOV STS A
Op Code 90H
290414 –7
1
D
7
0
0
1
0
0
0
0
D
0
EN FLAGS
Op Code 0F5H
1
D
7
1
1
1
0
1
0
1
D
0
3
RD and WR are edge triggered IBF OBF F
1
and
INT change internally after the trailing edge of RD
or WR
During the time that the host CPU is reading the
status register the UPI is prevented from updat-
ing this register or is ‘locked out ’
5
P
26
and P
27
are port pins or DMA handshake
pins for use with a DMA controller These pins
default to port pins on Reset
If the ‘‘EN DMA’’ instruction has been executed
P
26
becomes the DRQ (DMA Request) pin A ‘‘1’’
written to P
26
causes a DMA request (DRQ is
activated) DRQ is deactivated by DACK
RD
DACK
WR or execution of the ‘‘EN DMA’’ in-
struction
290414 –6
DMA Handshake Capability
290414 –8
5
INTEL [ INTEL CORPORATION ]
