GMS90 Series
Pin Number
Input/
Symbol
Function
PLCC-
44
PDIP-
40
MQFP-
44
Output
The Address Latch Enable / Program pulse
Output pulse for latching the low byte of the address
during an access to external memory. In normal
operation, ALE is emitted at a constant rate of 1/6 the
oscillator frequency, and can be used for external
timing or clocking. Note that one ALE pulse is skipped
during each access to external data memory. This pin
is also the program pulse input (PROG) during
EPROM programming.
ALE /
PROG
33
30
27
O
In GMS9XC54/56/58:
If desired, ALE operation can be disabled by setting
bit 0 of SFR location 8EH. With this bit set, the pin is
weakly pulled high. The ALE disable feature will be
terminated by reset. Setting the ALE-disable bit has
no affect if the microcontroller is in external execution
mode.
EA / VPP
35
31
29
I
External Access Enable / Program Supply Voltage
EA must be external held low to enable the device to
fetch code from external program memory locations
0000H to FFFFH. If EA is held high, the device
executes from internal program memory unless the
program counter contains an address greater than its
internal memory size. This pin also receives the
12.75V programming supply voltage (VPP) during
EPROM programming.
Note;
however, that if any of the Lock bits are
programmed, EA will be internally
latched on reset.
Port 0
P0.0-P0.7
36-43
32-39
30-37
I/O
Port 0 is an 8-bit open-drain bidirectional I/O port.
Port 0 pins that have 1s written to them float and can
be used as high-impedance inputs.
Port 0 is also the multiplexed low-order address and
data bus during accesses to external program and
data memory. In this application it uses strong internal
pull-ups when emitting 1s. Port 0 also outputs the
code bytes during program verification in the
GMS97X5X. External pull-up resistors are required
during program verification.
VSS
VCC
N.C.
22
44
20
40
-
16
38
-
-
-
Circuit ground potential
Supply terminal
No connection
for all operating modes
1,12
23,34
6,17
28,39
10
Dec. 1998 Ver 3.0
HYNIX [ HYNIX SEMICONDUCTOR ]
