80C453 Datasheet, PDF (11/23 Pages) NXP Semiconductors – CMOS single-chip 8-bit microcontrollers

Philips Semiconductors
CMOS single-chip 8-bit microcontrollers
Preliminary specification
80C453/83C453/87C453
ODS is active low for output driver control. The OBF flag can be
programmed to be cleared on the negative or positive edge of ODS.
Can produce an IOB interrupt (see Figure 2).
IDS – Input data strobe for port 6. IDS is used to control the port 6
input latch and input buffer full flag (IBF) bit in the CSR. The input
data latch can be programmed to be transparent when IDS is low
and latched on the positive transition of IDS, or to latch only on the
positive transition of IDS. Correspondingly, the IBF flag is set on the
negative or positive transition of IDS. Can produce an IIB interrupt
(see Figure 2).
AFLAG – AFLAG is a bidirectional I/O pin which can be
programmed to be an output set high or low under program control,
or to output the state of the output buffer full flag. AFLAG can also
be programmed to be an input which selects whether the contents of
the output buffer, or the contents of the port 6 control status register
will output on port 6. This feature grants complete port 6 status to
external devices.
BFLAG – BFLAG is a bidirectional I/O pin which can be
programmed to be an output, set high or low under program control,
or to output the state of the input buffer full flag. BFLAG can also be
programmed to input an enable signal for port 6. When BFLAG is
used as an enable input, port 6 output drivers are in the
high-impedance state, and the input latch does not respond to the
IDS strobe when BFLAG is high. Both features are enabled when
BFLAG is low. This feature facilitates the use of the 87C453 in
bused multiprocessor systems.
CONTROL STATUS REGISTER
The control status register (CSR) establishes the mode of operation
for port 6 and indicates the current status of port 6 I/O registers. All
control status register bits can be read and written by the CPU,
except bits 0 and 1, which are read only. Reset writes ones to bits 2
through 7, and writes zeros to bits 0 and 1 (see Table 3).
CSR.0 Input Buffer Full Flag (IBF) (Read Only) – The IBF bit is
set to a logic 1 when port 6 data is loaded into the input buffer under
control of IDS. This can occur on the negative or positive edge of
IDS, as determined by CSR.2. When IBF is set, the Interrupt Enable
Register bit IIB (IE.5) is set. The Interrupt Service Routine vector
address for this interrupt is 002BH. IBF is cleared when the CPU
reads the input buffer register.
CSR.1 Output Buffer Full Flag (OBF) (Read Only) – The OBF flag
is set to a logic 1 when the CPU writes to the port 6 output data
buffer. OBF is cleared by the positive or negative edge of ODS, as
determined by CSR.3. When OBF is cleared, the Interrupt Enable
Register bit IOB (IE.6) is set. The Interrupt Service Routine vector
address for this interrupt is 0033H.
CSR.2 IDS Mode Select (IDSM) – When CSR.2 = 0, a low-to-high
transition on the IDS pin sets the IBF flag. The Port 6 input buffer is
loaded on the IDS positive edge. When CSR.2 = 1, a high-to-low
transition on the IDS pin sets the IBF flag. Port 6 input buffer is
transparent when IDS is low, and latched when IDS is high.
CSR.3 Output Buffer Full Flag Clear Mode (OBFC) – When
CSR.3 = 1, the positive edge of the ODS input clears the OBF flag.
When CSR.3 = 0, the negative edge of the ODS input clears the
OBF flag.
CSR.4, CSR.5 AFLAG Mode Select (MA0, MA1) – Bits 4 and 5
select the mode of operation for the AFLAG pin as follows:
MA1
0
0
1
1
MA0
0
1
0
1
AFLAG Function
Logic 0 output
Logic 1 output
OBF flag output (CSR.1)
Select (SEL) input mode
The select (SEL) input mode is used to determine whether the port 6
data register or the control status register is output on port 6. When
the select feature is enabled, the AFLAG input controls the source of
port 6 output data. A logic 0 on AFLAG input selects the port 6 data
register, and a logic 1 on AFLAG input selects the control status
register.
The value of the AFLAG input is latched into the Auxiliary Register
(AUXR) bit 1 (AUXR.1). Checking this bit (AF) will allow the
87C453’s program to determine if Port 6 was loaded with data or a
UPI command.
CSR.6, CSR.7 BFLAG Mode Select (MB0, MB1) – Bits 6 and 7
select the mode operation as follows:
MB1 MB0
0
0
0
1
1
0
1
1
BFLAG Function
Logic 0 output
Logic 1 output
IBF flag output (CSR.0)
Port enable (PE)
In the port enable mode, IDS and ODS inputs are disabled when
BFLAG input is high. When the BFLAG input is low, the port is
enabled for I/O.
Reduced EMI Mode – The on–chip clock distribution drivers have
been identified as the cause of most of the EMI emissions from the
80C51 family. By tailoring the clock drivers properly, a compromise
between maximum operating speed and minimal EMI emissions can
be achieved. Typically, an order in magnitude of reduction is
possible over previous designs. This feature has been implemented
on this chip along with the additional capability of turning off the ALE
output. Setting the AO bit (AUXR.0) in the AUXR special function
register will disable the ALE output. Reset forces a 0 into AUXR.0 to
enable normal 80C51 type operation.
Auxiliary Register (AUXR)
7
6
5
4
3
2
1
0
–
–
–
–
–
–
AF AO
Latched value of AFLAG when Port 6
inputs data from IDS strobe
0 = ALE enabled
1 = ALE disabled
1996 Aug 15
3-321