Datasheet

22
3286P–MICRO–3/10
AT89S8253
Table 13-1. PCON – Power Control Register
PCON Address = 87H Reset Value = 00xx 0000B
Bit Addressable
SMOD1 SMOD0 – POF GF1 GF0 PD IDL
Bit7 6543210
Symbol Function
SMOD1 Double Baud Rate bit. Doubles the baud rate of the UART in Modes 1, 2, or 3.
SMOD0 Frame Error Select. When SMOD0 = 1, SCON.7 is SM0. When SMOD0 = 1, SCON.7 is FE. Note that FE will be set after
a frame error regardless of the state of SMOD0.
POF Power Off Flag. POF is set to “1” during power up (i.e. cold reset). It can be set or reset under software control and is not
affected by RST (i.e. warm reset).
GF1, GF0 General-purpose Flags
PD Power-down bit. Setting this bit activates power-down operation.
IDL Idle Mode bit. Setting this bit activates Idle mode operation
Table 13-2. SCON – Serial Port Control Register
SCON Address = 98H Reset Value = 0000 0000B
Bit Addressable
SM0/FE SM1 SM2 REN TB8 RB8 T1 RI
Bit7 6543210
(SMOD0 = 0/1)
(1)
Symbol Function
FE
Framing error bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not cleared by valid
frames but should be cleared by software. The SMOD0 bit must be set to enable access to the FE bit. FE will be set
regardless of the state of SMOD0.
SM0 Serial Port Mode Bit 0, (SMOD0 must = 0 to access bit SM0)
SM1
Serial Port Mode Bit 1
SM2
Enables the Automatic Address Recognition feature in modes 2 or 3. If SM2 = 1 then Rl will not be set unless the received
9th data bit (RB8) is 1, indicating an address, and the received byte is a Given or Broadcast Address. In mode 1, if SM2 =
1 then Rl will not be activated unless a valid stop bit was received, and the received byte is a Given or Broadcast Address.
In Mode 0, SM2 should be 0.
REN Enables serial reception. Set by software to enable reception. Clear by software to disable reception.
TB8 The 9th data bit that will be transmitted in modes 2 and 3. Set or clear by software as desired.
RB8
In modes 2 and 3, the 9th data bit that was received. In mode 1, if SM2 = 0, RB8 is the stop bit that was received. In mode
0, RB8 is not used.
TI
Transmit interrupt flag. Set by hardware at the end of the 8th bit time in mode 0, or at the beginning of the stop bit in the
other modes, in any serial transmission. Must be cleared by software.
RI
Receive interrupt flag. Set by hardware at the end of the 8th bit time in mode 0, or halfway through the stop bit time in the
other modes, in any serial reception (except see SM2). Must be cleared by software.
SM0 SM1 Mode Description Baud Rate
(2)
0 0 0 shift register f
osc
/12
0 1 1 8-bit UART variable
1 0 2 9-bit UART f
osc
/64 or f
osc
/32
1 1 3 9-bit UART variable