5
GP2021
Pin No
Signal Name
Type
Description ARM System Mode
Description Standard Interface
Mode
2
POWER_GOOD
I
Power Monitor input. High for normal operation. Low forces the GP2021 into
Power Down mode.
3
NRESET_OP O
System Reset output (Active Low). Lasts for 4 MICRO_CLK cycles after all reset
conditions have cleared.
4
NARMSYS
I
Processor Mode Selection input. When Low, this input selects ARM System
mode. When High, Standard Interface mode is selected.
5
XIN
I
Crystal input connection to Real Time Clock.
6
XOUT
O
Crystal output connection from Real Time Clock.
7
TXA
O
Transmit Data output from Channel A of the Dual UART.
8
TXB
O
Transmit Data output from Channel B of the Dual UART.
9
RXA
1
Receive Data input to Channel A of the Dual UART. This pin acts as a master clock
input in Digital System Test mode.
10
RXB
I
Receive Data input to Channel B of the Dual UART. This pin acts as the Real Time
Clock reset in Digital System Test mode.
11
NROM / NC
O
ROM Chip Select output (Active Low).
Unused output. (Do not connect.)
12
NEEPROM / NC
O
EEPROM Chip Select output (Active Low)
Unused output. (Do not connect.)
13
NSPARE_CS / NC
O
Spare Chip Select output (Active Low).
Unused output. (Do not connect.)
16
NRAM / NC
O
RAM Chip Select output (Active Low).
Unused output. (Do not connect.)
17
NW0 / NC
O
Byte 0 Write Strobe output (Active Low).
Unused output. (Do not connect.)
18
NW1 / NC
O
Byte 1 Write Strobe output (Active Low).
Unused output. (Do not connect.)
19
NW2 / NC
O
Byte 2 Write Strobe output (Active Low).
Unused output. (Do not connect.)
20
NW3 / NC
O
Byte 3 Write Strobe output (Active Low).
Unused output. (Do not connect.)
21
NRD / NC
O
Read Data Strobe output (Active Low).
Unused output. (Do not connect.)
22
ARM_ALE / NC
O
ALE output to the microprocessor
Unused output. (Do not connect.)
(Active High). Controls the transparent
latches at the microprocessor address
outputs.
23
DBE / NC
O
Data Bus Enable output to the
Unused output. (Do not connect.)
microprocessor. When Low, places the
microprocessor data bus drivers in a
high impedance state.
24
ACCUM_INT
O
A free running interrupt to the microprocessor. It allows control of data transfer
between the accumulators in the correlator and the microprocessor. It is active
Low when configured for ARM System mode or Motorola mode and is active High
in Intel mode.
25
MEAS_INT
O
An interrupt to the microprocessor. It allows control of measurement data transfer
between the correlator and the microprocessor. It is active Low when configured
for ARM System mode or Motorola mode and is active High in Intel mode.
26
NBW / WRPROG
I
Byte/Word input from the
Write–Read Program input. In Intel
microprocessor. Low indicates a byte
mode, High selects 486 style
transfer, and High a word transfer.
interface and Low 186 style.
Unused in Motorola mode
27
NMREQ / DISCIP2
I
Memory Request input from the
Multi–purpose discrete input.
microprocessor. Low indicates that the
microprocessor requires a memory
access during the following cycle.
28
NOPC / NINTELMOT
I
Opcode fetch input from the
High selects Motorola mode and
microprocessor. Low indicates that an
Low Intel mode.
instruction is being fetched and High
that data is being transferred.
29
NRW / DISCIP3
I
Read/Write Select input from the
Multi–purpose discrete input.
microprocessor. Low indicates a read
cycle and High a write cycle.
30
MCLK / NC
O
Microprocessor Clock output
Unused output. (Do not connect.)
(nominally 20MHz). Its phases can be
stretched under control of the
Microprocessor Interface.