2
1.0 INTRODUCTION
The UT69RH051 is a radiation-tolerant 8-bit microcontroller
that is pin equivalent to the MCS-51 industry standard
microcontroller when in a 40-pin DIP. The UT69RH051’s static
design allows operation from 1Hz to 20MHz. This data sheet
describes hardware and software interfaces to the UT69RH051.
2.0 SIGNAL DESCRIPTION
VDD: +5V Supply voltage
VSS: Circuit Ground
Port 0 (P0.0 - P0.7): Port 0 is an 8-bit port. Port 0 pins are used
as the low-order multiplexed address and data bus during
accesses to external program and data memory. Port 0 pins use
internal pullups when emitting 1’s and are TTL compatible.
Port 1 (P1.0 - P1.7): Port 1 is an 8-bit bidirectional I/O port with
internal pullups. The output buffers can drive TTL loads. When
the Port 1 pins have 1’s written to them, they are pulled high by
the internal pullups and can be used as inputs in this state. As
inputs, any pins that are externally pulled low sources current
because of the pullups. In addition, Port 1 pins have the alternate
uses shown in table 1.
Port 2 (P2.0 - P2.7): Port 2 is an 8-bit port. Port 2 pins are used
as the high-order address bus during accesses to external Program
Memory and during accesses to external Data Memory that uses
16-bit addresses (i.e., MOVX@DPTR). Port 2 uses internal
pullups when emitting 1’s in this mode. During operations that
do not require a 16-bit address, Port 2 emits the contents of the
P2 Special Function Registers (SFR). The pins have internal
pullups and drives TTL loads.
Port 3 (P3.0 - P3.7): Port 3 is an 8-bit bidirectional I/O port with
internal pullups. The output buffers can drive TTL loads. When
the Port 3 pins have 1’s written to them, they are pulled high by
the internal pullups and can be used as inputs in this state. As
inputs, any pins that are externally pulled low sources current
because of the pullups. In addition, Port 3 pins have the alternate
uses shown in table 2.
Table 1. Port 1 Alternate Functions
Table 2. Port 3 Alternate Functions
Port
Pin
Alternate
Name
Alternate Function
P1.0
T2
External clock input to Timer/
Counter 2
P1.1
T2EX
Timer/Counter 2 Capture/Reload
trigger and direction control
P1.2
ECI
External count input to PCA
P1.3
CEX0
External I/O for PCA capture/
compare Module 0
P1.4
CEX1
External I/O for PCA capture/
compare Module 1
P1.5
CEX2
External I/O for PCA capture/
compare Module 2
P1.6
CEX3
External I/O for PCA capture/
compare Module 3
P1.7
CEX4
External I/O for PCA capture/
compare Module 4
Port
Pin
Alternate
Name
Alternate Function
P3.0
RXD
Serial port input
P3.1
TXD
Serial port output
P3.2
INT0
External interrupt 0
P3.3
INT1
External interrupt 1
P3.4
T0
External clock input for Timer 0
P3.5
T1
External clock input for Timer 1
P3.6
WR
External Data Memory write
strobe
P3.7
RD
External Data Memory read strobe
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