NS486SXL Datasheet, PDF (13/26 Pages) National Semiconductor (TI) – Optimized 32-Bit 486-Class Controller with On-Chip Peripherals for Embedded Systems

2.0 SXL Pin Description Tables (Continued)
TABLE 12. 16550 UART Pins (Continued)
Symbol
RI
Pins
27
Type
I
Function
Ring Indicator. When low, this input signal indicates that a telephone ringing
signal has been received by the MODEM or data set. The RI signal is a MODEM
status input whose condition can be tested by reading bit 6 (RI) of the MODEM
Status Register. Bit 6 is the complement of the RI signal. Bit 2 (TERI) of the
MODEM Status Register indicates whether the RI input signal has changed from
a low to high state since the previous reading of the MODEM Status Register.
Note: Whenever the CTS bit of the MODEM Status Register changes state, an interrupt is generated
if the MODEM Status Interrupt is enabled.
Note: Whenever the RI bit of the MODEM Status Register changes from a high to a low state, an in-
terrupt is generated if the MODEM Status Interrupt is enabled.
Symbol
T0
T1
TABLE 13. Timer Pins
Pins
31
32
Type
I/O
I/O
Function
Programmable Timer pin 0. This Bidirectional pin may be selected to control one
of the following four functions via bits 1-0 of the Timer I/O Control Register:
1) The GATE input into Timer 0.
2) The GATE input into Timer 1.
3) The OUT output from Timer 0.
4) The CLK input into Timer 1.
Programmable Timer pin 1. This Bidirectional pin may be selected to control one
of the following four functions via bits 3-2 of the Timer I/O Control Register:
1) The GATE input into Timer 0.
2) The GATE input into Timer 1.
3) The OUT output from Timer 1.
4) The CLK input into Timer 0.
TABLE 14. 3-Wire Serial I/O Pins
Symbol
SO
SI
SCLK
Pins
18
19
20
Type
I/O
I/O
O
Function
The Serial data Output signal for MICROWIRE.
The Serial data Input signal for MICROWIRE or the serial data I/O for Access.bus.
The Serial CLocK signal for MICROWIRE and Access.bus.
Note 1: For MICROWIRE Slave Mode, a pin must be selected to be the Chip Select Input.
13
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