UPI-41AH/42AH
Table 1. Pin Description
DIP
Pin
No.
PLCC
Pin
No.
Symbol
Type
Name and Function
TEST 0,
TEST 1
1
2
I
TEST INPUTS:
Input pins which can be directly tested using conditional branch
instructions.
FREQUENCY REFERENCE:
TEST 1 (T
1
) also functions as the event timer input (under
software control). TEST 0 (T
0
) is used during PROM programming and ROM/EPROM
verification. It is also used during Sync Mode to reset the instruction state to S1 and
synchronize the internal clock to PH1. See the Sync Mode Section.
39
43
XTAL 1,
XTAL 2
2
3
3
4
I
INPUTS:
Inputs for a crystal, LC or an external timing signal to determine the internal
oscillator frequency.
RESET
4
5
I
RESET:
Input used to reset status flip-flops and to set the program counter to zero.
RESET is also used during EPROM programming and verification.
SS
5
6
I
SINGLE STEP:
Single step input used in conjunction with the SYNC output to step the
program through each instruction (EPROM). This should be tied to
a
5V when not used.
This pin is also used to put the device in Sync Mode by applying 12.5V to it.
CS
6
7
I
CHIP SELECT:
Chip select input used to select one UPI microcomputer out of several
connected to a common data bus.
EA
7
8
I
EXTERNAL ACCESS:
External access input which allows emulation, testing and
ROM/EPROM verification. This pin should be tied low if unused.
RD
8
9
I
READ:
I/O read input which enables the master CPU to read data and status words from
the OUTPUT DATA BUS BUFFER or status register.
A
0
9
10
I
COMMAND/DATA SELECT:
Address Input used by the master processor to indicate
whether byte transfer is data (A
0
e
0, F1 is reset) or command (A
0
e
1, F1 is set). A
0
e
0
during program and verify operations.
WR
10
11
I
WRITE:
I/O write input which enables the master CPU to write data and command words
to the UPI INPUT DATA BUS BUFFER.
SYNC
11
13
O
OUTPUT CLOCK:
Output signal which occurs once per UPI instruction cycle. SYNC can
be used as a strobe for external circuitry; it is also used to synchronize single step
operation.
D
0
–D
7
(BUS)
12–19 14–21
I/O
DATA BUS:
Three-state, bidirectional DATA BUS BUFFER lines used to interface the UPI
microcomputer to an 8-bit master system data bus.
P
10
–P
17
27–34 30–33
I/O
PORT 1:
8-bit, PORT 1 quasi-bidirectional I/O lines. P
10
–P
17
access the signature row
and security bit.
35–38
P
20
–P
27
21–24 24–27
35–38 39–42
I/O
PORT 2:
8-bit, PORT 2 quasi-bidirectional I/O lines. The lower 4 bits (P
20
–P
23
) interface
directly to the 8243 I/O expander device and contain address and data information during
PORT 4–7 access. The upper 4 bits (P
24
–P
27
) can be programmed to provide interrupt
Request and DMA Handshake capability. Software control can configure P
24
as Output
Buffer Full (OBF) interrupt, P
25
as Input Buffer Full (IBF) interrupt, P
26
as DMA Request
(DRQ), and P
27
as DMA ACKnowledge (DACK).
PROG
25
28
I/O
PROGRAM:
Multifunction pin used as the program pulse input during PROM programming.
During I/O expander access the PROG pin acts as an address/data strobe to the 8243.
This pin should be tied high if unused.
V
CC
40
44
POWER:
a
5V main power supply pin.
V
DD
26
29
POWER:
a
5V during normal operation.
a
12.5V during programming operation. Low
power standby supply pin.
V
SS
20
22
GROUND:
Circuit ground potential.
3