Rainbow Electronics AT89C5122 - Manual (Page 161)

161
AT8xC5122/23
4202E–SCR–06/06
INT1 Interrupt Vector The INT1 interrupt is multiplexed with the following three inputs:
• INT1 : Standard 8051 interrupt input
• RXD : Received data on UART
• CPRES: Insertion or remove of the main card
The setting configurations for each input is detailed below.
INT1 Input This interrupt input is active under the following conditions :
• It must be enabled by OEEN Bit (ISEL Register)
• It can be active on a level or falling edge following IT1 Bit (TCON Register) status
• If level triggering selection is set, the active level 0 or 1 can be selected with OELEV
Bit (ISEL Register)
The Bit IE1 (TCON Register) is set by hardware when external interrupt detected. It is
cleared when interrupt is processed.
RXD Input A second vector interrupt input is the reception of a character. UART Rx input can gen-
erate an interrupt if enabled with Bit RXEN (ISEL.0). The global enable bits EX1 and EA
must also be set.
Then, the Bit RXIT (ISEL Register) is set by hardware when a low level is detected on
P3.0/RXD input.
CPRES Input The third input is the detection of a level change on CPRES input (P1.2). This input can
generate an interrupt if enabled with PRESEN (ISEL.1) , EX1 (IE0.2) and EA (IE0.7)
Bits.
This detection is done according to the level selected with Bit CPLEV (ISEL.7).
Then the Bit PRESIT (ISEL.5) is set by hardware when the triggering conditions are
met. This Bit must be cleared by software.