AT89C5132 Atmel Corporation, AT89C5132 Datasheet - Page 24

• Manufacturer Part Number: AT89C5132
• Manufacturer: Atmel Corporation

Specifications of AT89C5132

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-12C
• Max I/o Pins: 44
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Uart: 1
• Adc Channels: 2
• Adc Resolution (bits): 10
• Adc Speed (ksps): 22.7
• Sram (kbytes): 2.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 3.6
• Timers: 2
• Isp: UART/USB
• Watchdog: Yes

8.2.2
8.2.3
24
AT89C5132
Page Access Mode
External Bus Cycles
Figure 8-3 shows the structure of the external address bus. P0 carries address A7:0 while P2
carries address A15:8. Data D7:0 is multiplexed with A7:0 on P0. Table 12 describes the exter-
nal memory interface signals.
Figure 8-3.
Table 12. External Data Memory Interface Signals
The AT89C5132 implement a feature called Page Access that disables the output of DPH on P2
when executing MOVX @DPTR instruction. Page Access is enable by setting the DPHDIS bit in
AUXR register.
Page Access is useful when application uses both ERAM and 256 Bytes of XRAM. In this case,
software modifies intensively EXTRAM bit to select access to ERAM or XRAM and must save it
if used in interrupt service routine. Page Access allows external access above 00FFh address
without generating DPH on P2. Thus ERAM is accessed using MOVX @Ri or MOVX @DPTR
with DPTR < 0100h, < 0200h, < 0400h or < 0800h depending on the XRS1:0 bits value. Then
XRAM is accessed using MOVX @DPTR with DPTR ≥ 0800h regardless of XRS1:0 bits value
while keeping P2 for general I/O usage.
This section describes the bus cycles that AT89C5132 executes to read (see Figure 8-4), and
write data (see Figure 8-5) in the external data memory.
Signal
Name
AD7:0
A15:8
ALE
WR
RD
Type
I/O
O
O
O
O
External Data Memory Interface Structure
Description
Address Lines
Upper address lines for the external bus.
Address/Data Lines
Multiplexed lower address lines and data for the external memory.
Address Latch Enable
ALE signals indicates that valid address information are available on lines AD7:0.
Read
Read signal output to external data memory.
Write
Write signal output to external memory.
AT89C5132
ALE
WR
RD
P2
P0
AD7:0
A15:8
Latch
A7:0
A15:8
A7:0
D7:0
OE
WR
PERIPHERAL
RAM
4173E–USB–09/07
Alternate
Function
P2.7:0
P0.7:0
P3.7
P3.6
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