SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 160

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Figure 8-8
Special Function Register CTCON (Address 0E1 H )
Bit
CTF
All of these bits that generate interrupts can be set or cleared by software, with the same result as
if they had been set or cleared by hardware. That is, interrupts can be generated or pending
interrupts can be cancelled by software. The only exceptions are the request flags IE0 and lE1. lf
the external interrupts 0 and 1 are programmed to be level-activated, IE0 and lE1 are controlled by
the external source via pin INT0 and INT1, respectively. Thus, writing a one to these bits will not set
the request flag IE0 and/or lE1. In this mode, interrupts 0 and 1 can only be generated by software
and by writing a 0 to the corresponding pins INT0 (P3.2) and INT1 (P3.3), provided that this will not
affect any peripheral circuit connected to the pins.
Each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit
in the special function registers IEN0, IEN1 and IEN2 (figures 8-2, 8-3 and 8-4). Note that IEN0
contains also a global disable bit, EAL, which disables all interrupts at once. Also note that in the
SAB 8051 the interrupt priority register IP is located at address 0B8 H ; in the SAB 80C517 this
location is occupied by register IEN1.
1) Only available in SAB 80C517 identification mark ’BB’ or later.
Semiconductor Group
0E1 H
T2PS1
Function
Compare timer overflow. Set by hardware at a rollover of the compare timer. Bit
is cleared by hardware (since CA-step; cleared by software in BC-step and
earlier versions). If the compare timer interrupt is enabled. CTF = 1 will cause an
interrupt.
These bits are not used for interrupt control.
1)
–
–
–
161
CTF
CLK2
CLK1
Interrupt System
CLK0
CTCON