TS80C54X2/C58X2
TS87C54X2/C58X2
XTAL1
XTAL1:2
X2 bit
CPU clock
STD Mode
X2 Mode
STD Mode
Figure 2. Mode Switching Waveforms
The X2 bit in the CKCON register (See Table 4.) allows to switch from 12 clock cycles per instruction to 6 clock
cycles and vice versa. At reset, the standard speed is activated (STD mode). Setting this bit activates the X2 feature
(X2 mode).
CAUTION
In order to prevent any incorrect operation while operating in X2 mode, user must be aware that all peripherals
using clock frequency as time reference (UART, timers) will have their time reference divided by two. For example
a free running timer generating an interrupt every 20 ms will then generate an interrupt every 10 ms. UART with
4800 baud rate will have 9600 baud rate.
8
Rev. B - Aug. 31, 1999
TEMIC [ TEMIC SEMICONDUCTORS ]
