The SC400 is a 66Mhz System-On-Chip produced by AMD. It is powering devices such as the usr2450, the RG1000, or others.
JTAG pins on the PC Card Socket A
— PC card socket A
TCK : in bit; — This is also MCELA, which is an output
TMS : in bit; — This is also MCEHA, which is an output
TDI : in bit; — This is also RSTA, which is an output
TDO : out bit; — This is also REGA, which is an output
The manual also makes reference to JTAG pins multiplexed on the PC card controller:
Five pins— BNDSCN_TDI, BNDSCN_TMS, BNDSCN_TCK, BNDSCN_TDO, and BNDSCN_EN. On the ÉlanSC400 microcontroller, only the BNDSCN_EN pin is dedicated; the other four are multiplexed with the PC Card controller signals. All five boundary-scan interface pins are dedicated on the ÉlanSC410 microcontroller.
Another 21096.pdf has the TDI (RSTA - pin58), TDO (REGA# - pin61), TMS (MCEHA# - pin42), TCK (MCELA# - pin7) pins identified: