UP-5900VS
CIRCUIT DESCRIPTION
5 – 41
PD7-0
82-75
Parallel Port
I/O
Group 9
Parallel Port Data – These bidirectional signals transfer data to and from the peripheral
data bus and the appropriate parallel port data register. These signals have a high cur-
rent drive capability.
PE
70
Parallel Port
Input
Group 2
Group 3
Paper End – This input signal is set high by the printer when it is out of paper. This pin
has an internal weak pull-up or pull-down resistor.
RDATA
54
FDC
Input
Group 1
Read Data – This input signal holds raw serial data read from the Floppy Disk Drive
(FDD).
RI2,1
97,87
UART1
Input
Group 1
Ring Indicators (Modem) – When low, this signal indicates that a telephone ring signal
has been received by the modem.
The RI1 and RI2 pins have schmitt-trigger input buffers.
RI2 is multiplexed with DENSEL and available only in Two-UART mode.
RTS2,1
98,88
UART1,
UART2
Output
Group 12
Request to Send – When low, these output signals indicate to the modem or other data
transfer device that the corresponding UART1 or UART2 is ready to exchange data.
A Master Reset (MR) sets RTS to inactive high. Loopback operation holds it inactive.
RTS2 is multiplexed on pin 98 with IRSL1 and ID1, and available only in Two-UART
mode. RTS1 is multiplexed on pin 88 with BADDR1.
SIN2,1
99,89
UART1,
UART2
Input
Group 1
Serial Input – This input signal receives composite serial data from the communications
link (peripheral device, modem or other data transfer device).
SIN2 is multiplexed on pin 99 with ID3 and available only in Two-UART mode.
SLCT
69
Parallel Port
Input
Group 2
Select – This input signal is set active high by the printer when the printer is selected.
This pin is internally connected to a nominal 25K
Ω
pull-down resistor.
SLIN
73
Parallel Port
I/O
Group 8
Select Input – When this signal is active low it selects the printer.
This signal is in TRI-STATE after a 0 is loaded into the corresponding control register
bit. Use an external 4.7 KW pull-up resistor.
This signal is multiplexed with ASTRB.
SOUT2,1
100,92
UART1,
UART2
Output
Group 12
Serial Output – This output signal sends composite serial data to the communications
link (peripheral device, modem or other data transfer device).
The SOUT2,1 signals are set active high after a Master Reset (MR).
SOUT2 is multiplexed on pin 100 with IRRX2, IRSL0 and ID0, and is available only in
Two-UART mode.
SOUT1 is multiplexed on pin 92 with CFG0.
STB
67
Parallel Port
I/O
Group 8
Data Strobe – This output signal indicates to the printer that valid data is available at
the printer port.
This signal is in TRI-STATE after a 0 is loaded into the corresponding control register
bit.
An external 4.7 K
Ω
pull-up resistor should be employed.
This signal is multiplexed with WRITE.
STEP
51
FDC
Output
Group 11
Step – This output signal issues pulses to the disk drive at a software programmable
rate to move the head during a seek operation.
TC
25
ISA-Bus
Input
Group 1
DMA Terminal Count – The DMA controller issues TC to indicate the termination of a
DMA transfer. TC is accepted only when a DACK signal is active.
TC is active high in PC-AT mode, and active low in PS/2 mode.
TRK0
55
FDC
Input
Group 1
Track 0 – This input signal indicates to the controller that the head of the selected
floppy disk drive is at track 0.
VDD
90,41
Power
Supply
Input
Main 5 V Power Supply – This signal is the 5 V supply voltage for the digital circuitry.
VSS
91,65,40, 15
Power
Supply
Output
Ground – This signal provides the ground for the digital circuitry.
WAIT
66
Parallel Port
Input
Group 2
Wait – In EPP mode, the parallel port device uses this signal to extend its access cycle.
WAIT is active low. This signal is multiplexed with BUSY.
WDATA
49
FDC
Output
Group 11
Write Data (FDC) – This output signal holds the write precompensated serial data that
is written to the selected floppy disk drive. Precompensation is software selectable.
WGATE
53
FDC
Output
Group 11
Write Gate (FDC) – This output signal enables the write circuitry of the selected disk
drive. WGATE is designed to prevent glitches during power up and power down. This
prevents writing to the disk when power is cycled.
WP
57
FDC
Input
Group 1
Write Protected – This input signal indicates that the disk in the selected drive is write
protected.
WRITE
67
Parallel Port
Output
Group 8
Write Strobe – In EPP mode, this active low signal is a write strobe. This signal is mul-
tiplexed with STB.
Signal/Pin
Name
Pin Number
Module
I/O and
Group #
Function
